If we carefully analyze the Torah reading (Vayikra 22:26-23:44), we readily note that the yomim tovim are prefaced by the pasuk (23:4), "These are the holy occasions which you shall designate in their seasons", and a corresponding conclusion of (ibid. 37) "These are the festivals of God which you shall appoint as holy occasions...", follows the pesukim about the days and sacrifices of Sukkos (the final holiday in the portion). However, Sukkos stands out from the other yomim tovim, as the Torah does not present the mitzvos of Sukkos in the main body of text about the holidays. Rather, after presenting a few very general facts about Sukkos, and concluding, "These are the festivals...", the Torah then says (ibid. 39-43), "However, on the fifteenth day of the seventh month (Tishrei)...you shall celebrate...and you shall take to yourselves on the first day a beautiful fruit...You shall dwell in sukkos for seven days..." Why are the commandments of Sukkos excluded from the main text and presented as an addendum? Why does the Torah close the section about yomim tovim with a generic conclusion after presenting the generalities of Sukkos and then go back to Sukkos and enumerate its mitzvos?
I really do not want to confuse anyone (especially myself), but I must also ask why it is that the historical background of Sukkos is not portrayed, or even alluded to, in the Torah. Other seemingly less important events are given full attention, whereas Sukkos, which represents (Gemara Sukkah 11b) the clouds of glory (according to Rabbi Eliezer) or actual protective booths (according to Rabbi Akiva) is the basis for an entire set of commandments, and we do not even know about the historical fundamentals of its background, save from the verses which themselves present the festival's requirements. It is precisely this elusiveness which gives rise to the Talmudic dispute concerning what exactly the sukka represents. Why, then, is the background of Sukkos not detailed in the Torah?
If we think about the first problem raised above (the Torah text's layout of the festivals and the unusual presentation of Sukkos), we can suggest a solution which sheds much light on the overall uniqueness of this holiday. Whereas all other yomim tovim are commemorated on their respective dates by observances which relate to those very dates, the mitzvos of Sukkos correspond to no historic date. The first of Tishrei is the anniversary of Creation (or God's plan for Creation) and is historically a day of universal judgment, and we recognize it as such by blowing the shofar and observing the rites of yom tov. The same is true of the fifteenth the Nisan (Pesach), which is the anniversary of the Exodus, and is thus aptly commemorated by the mitzvos of the seder night, etc. Sukkos has no historic date. The sheltering of Bnei Yisroel in the desert was ongoing and attached to no point in time. Thus, the mitzvos of Sukkos, and its very nature, differ starkly from those of all other festivals. It is likely for this reason that the observances of Sukkos are not part of the verses which summarize the festival and are relegated to pesukim afterwards.
Still, we can ask why Sukkos is mandated at all. Other acts of God's protection and caretaking have not earned the status of festivals (such as the provision of manna, Miriam's well, etc.); why is Sukkos different?
It would seem that the answer lies in Rabbi Akiva's explanation as to what the "sukkos" referenced in the Torah really were. Rabbi Akiva maintains that sukkos were protective booths which the Jews "made for themselves" (Gemara ibid.). This sounds strange -God established a yom tov to commemorate what humans built?
I think that Rabbi Akiva's clear intent was that we commemorate God's protection, albeit that it was experienced in man-made structures. (Rabbi Eliezer also recognizes that our sukka-dwelling reflects God's protection, but that he holds that the protection was in divinely-created shelters.) Rabbi Akiva must maintain, however, that the uniqueness of the protection of the sukka is not just that it was a successful protective shelter which God enabled to hold up well and keep out harsh weather. This is hardly comparable with other miracles recorded in the Torah which were eternalized as yomim tovim. Rather, the divine sheltering of the sukka in the midbar was significant to merit establishment as a yom tov inasmuch as it was not just an act - it was an experience. Living in sukkos - in God's protective region - was a type of existence. It was the prototype of life in a spiritual realm, beyond the natural. Thus, Sukkos represents living in the midbar under Hashem's wings and in His shadow. It encompasses all of the divine caregiving throughout our travels, thus exceeding specific acts of benevolence (e.g. the well, manna, Bnei Yisroel's clothing not wearing out, etc.). Life in a sphere of holiness was not confined to any one date, and it receives no specific mention in the Torah, as the entirety of Jewish existence at the time was in the background and on the stage of life under God's protective aura, as we know from the totality of the Torah's treatment of Bnei Yisroel in the midbar.
In light if this, we can appreciate the deeper significance of the extraordinary textual treatment of Sukkos. The lack of a specific calendar date which differentiates it from other yomim tovim in the Torah reading represents that Sukkos is not an historic event; rather, it was and is a timeless state of existence. Thus, its inclusion in the parsha of "moadim" ["appointed times"] read on the first day of Sukkos is somewhat of an enigma, and its detailed treatment is purposefully differentiated.
It is thus also understood why the Beis Hamikdash is symbolized by the sukka in our liturgy. After the completion of travel though the midbar, life in a realm filled with God's holiness, as marked by regular, revealed miracles, ceased to exist in a large-scale framework. Henceforth, the Beis Hamikdash was to serve as such a place. There, one was able to enter the region of the Shechina and observe the miracles described in the Gemara on a continual basis. The Beis Hamikdash was the encapsulation of life in the midbar.
(It is abundantly clear as well why one may not desecrate the the sukka by bringing in certain types of objects [Sh. Aruch, O.C.639], as the sukka represents a place of God's presence. )
We can also understand why many kabalistic notions and rites (Ushpizin, Hoshana Rabba tefillos,etc.) are widely-practiced during Sukkos even by communities which generally do not recite kabalistic texts or maintain kabalistic rituals. As on Sukkos, that which is hidden ("sod" - including Kabala) from normative existence becomes revealed, as we are privileged to dwell in God's sanctum and experience things more from an insider's perspective. Whereas non-Chassidic Ashkenazic and Western Sephardic mesorah (tradition) posits that Kabala is reserved for those who are on levels of kedusha fit to be privy to its teachings and practices, such mesora allows for laymen to recite kabalistic prayers on Sukkos, as all of us have been granted entry to God's palace and are thus living on the inside, so to speak.
It is noteworthy that Sukkos occurs shortly after the Yomim Noroim. This sequence represents moving from the soul-cleansing of Yom Kippur into the sanctity of the sukka, similar to one who undergoes purification prior to entering the Beis Hamikdash.
Let's conclude with an analysis of the dispute of Rabbi Eliezer and Rabbi Akiva as to what the sukka commemorates. It would at first seem to be a point of mere historical value. However, the crux of the argument is extremely profound. It may be that Rabbi Eliezer maintains that the historical sukka experience was akin to that of the balance of life in the midbar. Just as all of the other miracles, as well as seeing God's revelation at Sinai, were an educational process, in which Bnei Yisroel were imbued with deep emuna and commitment to Hashem and His Torah, regular life was in totality such an experience. It was a time in which God performed open miracles even when the result could have been attained by "natural" means, and the clouds of glory were not an exception to this theme. Rabbi Akiva perhaps holds that the educational process of the midbar was one of encouraging the Jews to invest of themselves in order to deserve God's miraculous benevolence, and it was thus necessary for the people to put forth effort first (building dwellings) as a sign of their trust in Hashem's protection and salvation (as at the Yam Suf, the various wars, etc.) Although both ideas are true, Rabbi Eliezer and Rabbi Akiva argue concerning whether the Jewish People's "hishtadlus" (efforts) were the means by which they deserved God's miracles or whether such effort was part of the educational faith-training itself as it comprised the desert experience.
May we merit to dwell in God's sukka with full trust in Him and His hashgacha (providence) over all. May the permanent sukka in Yerushalayim soon be rebuilt.