And the children of Israel were fruitful and had many children. And they multiplied and became very mighty. And the land was filled with them. (Shemot 1:7)
The opening pesukim of Sefer Shemot list the sons of Yaakov. The Chumash explains that Yosef and his brothers died in Egypt and that in Egypt in exile, Bnai Yisrael grew into a large and mighty nation.
Rabbaynu Ovadia Sforno explains that during the lifetime of Yosef and his brothers, Bnai Yisrael emulated the example of these tzadikim – righteous individuals. The people were committed to lives of truth and morality and their descendents emulated them. However, with the passing of these inspirational characters, the behavior of their descendants began to deteriorate. This moral corruption was responsible for their bondage. In other words, Bnai Yisrael became enslaved to the Egyptians as a consequence of their abandonment of the values of their ancestors.
Sforno does acknowledge that the exile of Bnai Yisrael was the realization of a Divine decree upon the Jewish people. It was predetermined. However, this decree did not include bondage and suffering. The suffering of Bnai Yisrael in Egypt was a punishment for the sinful behavior of the people.
Sforno’s position presents an obvious problem. Earlier, in Parshat Lech Lecha, Hashem revealed to Avraham that his descendants would be exiled to a foreign land; they would be oppressed in that land, and finally, they would be redeemed. This prophecy was a reference to the exile in Egypt. This prophecy seems to contradict Sforno’s contention that the oppression experienced by Bnai Yisrael was not preordained. If the bondage and oppression was not predetermined, how could Hashem tell Avraham that his children would suffer Egypt?
Sforno explains that Hashem’s message to Avraham does not indicate that the fate of the people was preordained. They sinned of their own volition and this behavior caused the bondage. Hashem knows the future with complete clarity and through means we cannot understand. Hashem’s knowledge does not imply preordination.
This explanation reconciles Hashem’s message to Avraham with Sforno’s contention that bondage and suffering were not preordained. However, the answer gives rise to a further question. Why then did Hashem share this information with Avraham? If the bondage and oppression of Bnai Yisrael were not preordained, why did Hashem include these elements in His description of the nation’s future?
Sforno responds that this message was given to Avraham for transmission to his descendants. The prophecy would serve as evidence that the suffering of the people was not merely an arbitrary nuance of fate. Hashem had revealed to Avraham that this punishment would occur. Because of this revelation, the people would know that their suffering was not the result of chance events. They would know that Hashem was aware of and had foretold their oppression. This would lead them to search for the reason for their suffering and hopefully to the realization that the deterioration in the nation’s relationship with G-d was the basis for the bondage. This would suggest a means to end the suffering. Repentance could save the people. Without the message transmitted through Avraham, the people might conclude that they were the victims of political or sociological forces and that repentance could not help. Avraham’s prophecy disproved this assumption. 
Moshe was the first prophet to act as Hashem’s spokesman
And Moshe answered: They will not believe me and they will not obey my voice. For they will say, “Hashem has not appeared to you.” (Shemot 4:1)
Hashem directs Moshe to address Bnai Yisrael. He is to reveal to them his mission. He is to tell them that Hashem will redeem them from Egypt. Through Moshe, Hashem will take Bnai Yisrael out of Egypt and lead them to the Land of Israel. Moshe protests. The people will not follow him. They will not believe that Hashem has spoken to him. Certainly, they will not follow him through the wilderness to the Land of Israel.
Moshe's objections are difficult to understand. Moshe was not the first prophet. Hashem had spoken to the forefathers and others. None of these prophets raised Moshe's objections. They did not contend that their prophecies would be denied or that they would be dismissed as madmen. Why did Moshe bring up these issues?
Maimonides deals with this question in his Moreh Nevuchim. He offers an amazing answer. Maimonides begins by explaining that Moshe's objections were completely appropriate. He was to represent himself as Hashem’s emissary. The nation should require Moshe to provide credentials. They would be fools if they followed Moshe without proof of his authenticity. Moshe recognized the legitimacy of Bnai Yisrael’s suspicions.
Therefore, he asked Hashem to provide him with the means to verify his authenticity.
Based on this analysis, Maimonides reformulates our question. We cannot criticize Moshe's concerns. However, we must ask a different question. Why did previous prophets not raise these issues? Why did Avraham not ask Hashem for some means to confirm his authenticity?
Maimonides explains that Moshe was different from previous prophets. Previous prophets received prophecies aimed at guiding them towards their own personal perfection. Alternatively, their prophecies provided knowledge of their destiny or the future of their progeny. The people did not require these prophets to prove their authenticity. They did not speak to the people in the name of Hashem. Maimonides further explains that Avraham did not speak to humanity as Hashem's spokesman. He addressed humankind as a teacher. He provided instruction based upon reason and argument. He presented rational proofs for his theology and philosophy. Therefore, Avraham did not need to prove his prophetic status to the people. He never insisted that he be followed and obeyed as Hashem's spokesman. Moshe was the first prophet instructed to address a nation on behalf of Hashem. Moshe was to reveal Hashem's will and act as His spokesman. Moshe needed proof. He was confronted with a different and new mission. This mission required that he prove his authenticity. 
Moshe’s bewilderment with Hashem’s silence
And Moshe returned to Hashem and he said: G-d, why have you mistreated this nation? Why have you sent me? (Shemot 5:22)
Moshe goes to Paroh. He tells Paroh that Hashem has commanded Bnai Yisrael to go out to the wilderness and worship Him. Paroh refuses to allow Bnai Yisrael to travel into the wilderness or worship Hashem. Furthermore, Paroh increases the burden of Bnai Yisrael. He demands more labor from them. Moshe is troubled by this outcome. In our pasuk, Moshe addresses Hashem. He recounts that Hashem told him that Bnai Yisrael would be redeemed. He sent him to Paroh to demand their freedom. Moshe had dutifully followed Hashem's directions. However, he had failed to achieve any positive result. Instead, Moshe's actions had increased the suffering of the nation! How can this outcome be reconciled with Hashem's promise to redeem His nation?
The commentaries are troubled by Moshe's question. Hashem had revealed to Moshe that Paroh would not acquiesce to his request. Paroh would only relent as a result of overpowering plagues. Moshe should not have been surprised by Paroh's response. The required plagues had not yet begun!
Rabbaynu Avraham ibn Ezra offers an interesting response. The final redemption would be the exodus from Egypt. Moshe understood that this ultimate step would require overwhelming force. Moshe understood that this final stage of rescue had not yet arrived. However, Moshe expected some immediate improvement in the condition of Bnai Yisrael. In other words, he assumed that redemption would be a process. The final step would only be secured through the plagues. But the process would begin immediately. Therefore, Moshe was shocked by the deterioration in Bnai Yisrael's condition.
Nachmanides explains Moshe's question differently. Moshe understood that Paroh would only respond to force. He was not surprised that Paroh increased his torment of the Jewish people. But he was shocked that Hashem did not respond and punish Paroh. Moshe expected the plagues to begin immediately. Instead, Hashem was silent. Moshe was puzzled. If the time had come for redemption, let the process begin. If the moment of redemption had not yet arrived, why had he been sent to Egypt? Moshe had spoken to the people of their salvation but not produced any positive results. This could only undermine Moshe's credibility.
 Rabbaynu Ovadia Sforno, Commentary on Sefer Beresheit, 13:13.
 Rabbaynu Moshe ben Maimon (Rambam / Maimonides) Moreh Nevuchim, volume 1, chapter 63.
 Sefer Shemot 3:20.
 Rabbaynu Avraham ibn Ezra, Commentary on Sefer Shemot, 5:22-23.
 Rabbaynu Moshe ben Nachman (Ramban / Nachmanides), Commentary on Sefer Shemot 5:22.