Moosaa’s call was directed to tawheed, NOT to gain rulership and authority’

Moosaa, the one to whom Allaah spoke directly, the strong and trustworthy.
We see that his call was directed to tawheed and carried the lights of guidance and wisdom. Moosaa was brought up and was raised in the palaces of the greatest tyrant who claimed divinity. He knew the various types of corruption, unbelief, tyranny, injustice and despotism from what he witnessed in the palaces. He saw things which it is difficult to imagine or think possible. He also saw the enslavement of his people, the Children of Israa’eel, and their humiliation, and their women taken as slaves, and the killing of their children, to such an extent that it surpassed any oppression known to mankind. Allaah, the Most High, says,
“Pharaoh exalted himself haughtily in the land, and divided its people into castes. He enslaved a group of them (i.e., the Children of Israa’eel), killing their sons and letting their women live. He was indeed one of the corrupt evil-doers.”[1]
The people of Pharaoh were also people of shirk and idol-worship without a doubt.
So how did Moosaa begin? Was his call directed to correction of the ‘aqeedah of this idolatrous nation? Or did it begin with a demand for the restoration of the rights of the Children of Israa’eel, and a struggle to gain rulership and authority from the hands of the tyrant, and at the head of them Pharaoh, who claimed divinity for himself?
The call of Moosaa was just like the call of his forefathers and brothers from the earlier Prophets. His Lord instructed him and inspired him with the principle of tawheed, and chose him to carry his revelation, and to establish worship of Him. Allaah, the Most High, says,
“Has not the story of Moosaa come to you? When he saw a fire and said to his family, ‘Remain where you are for I have seen a fire. Perhaps I can bring a fire-brand from it or find someone who can show us the way.’ So when Moosaa came to the fire his Lord called him, ‘O Moosaa, I am your Lord. Remove your shoes, indeed you are in the purified valley of Tuwaa. I have chosen you as My Messenger, so listen to and heed what I reveal to you. Indeed I am Allaah. None has the right to be worshipped but Me. So worship Me and do not worship anything else besides Me, and establish Prayer for My remembrance. Indeed the Final Hour is certainly coming, which I keep hidden from all except Myself, in order to reward each soul according to its good or bad deeds.’”[2]
So this was the beginning of his Messengership; he was inspired and ordered with the ‘aqeedah of tawheed. He was ordered to establish it in himself and to represent it in his life. Then he was entrusted with the duty of calling to this sublime principle and was sent by Allaah to the Pharaoh. Allaah furthermore explained to him the correct manner of giving da’wah and the wise way in which he was to face the Pharaoh. Allaah, the Most High, said: 
“Go to Pharaoh who has transgressed all bounds in his haughtiness, pride, unbelief, and say, ‘Will you not purify yourself from the sin of unbelief and be obedient to your Lord? And that I guide you to the worship of your Lord, so that you may submit fearfully to Him and obey Him.’”[3]
He also supported him with his brother Haaroon in order for the proof to be established to the utmost, and He taught them to use gentleness and mildness in da’wah since that is the best way to attain the guidance of those whom Allaah wishes to guide:
“Go both of you to Pharaoh, indeed he has transgressed beyond all bounds, and speak mildly with him that he might accept admonition and fear and be obedient to his Lord.”[4]
So they carried out the order of their Lord and called him to Allaah, hoping for him to be guided and purified, so that he should be one of those who fear Allaah and fear and beware of the evil consequences of shirk and oppression. But he did not respond to this wise and composed call. So Moosaa manifested the great signs and clear proofs of his Prophethood and the truthfulness of his Messengership. But the despotic tyrant Pharaoh merely increased in his transgression and rejection of the truth:
“But Pharaoh denied the signs which Moosaa came with and disobeyed his order for him to fear and obey his Lord. Then he turned away from what he ordered him (i.e., obedience to his Lord) and instead worked evil and corruption, and he gathered his people and his followers and said, ‘I am your lord, the most high.’ So Allaah seized him with punishment for his latter and his earlier saying.”[5] 
The Escalation of the Tyranny of the Pharaoh and how Moosaa and his People Faced it with Patient Perseverance and Forbearance
“The chiefs of Pharaoh’s people said, ‘Will you leave Moosaa and his people to cause mischief in the land when they have abandoned worship of you and worship of your gods?’ He said, ‘We will kill their sons and let their women live, and will have full power over them.’”[6]
So what was the sin of Moosaa and his people in the view of these criminals? No crime except that they called to the tawheed of Allaah and to remain firm upon it, and to disbelieve in Pharaoh and his idols. Then what was the response of Moosaa with respect to these disgraceful and outrageous transgressions which exceeded all bounds in its barbarity and ferocity?!
His response was to remain firm upon correct belief, and to have patience and forbearance, and to seek the aid of Allaah in facing these calamities. Then he awaited the good outcome, and victory as a consequence and a good fruit of this remaining firm and this patient perseverance.
“Moosaa said to his people, ‘Seeks Allaah’s help and be patient, the earth is Allaah’s, He gives it as a heritage to whom He pleases from His servants. The final outcome is in favour of those who fear Allaah by avoiding disobedience of Him and doing what He orders.’”[7]
Then when no hope that the Pharaoh and his people would believe remained, and the suffering which the Children of Israa’eel were subjected to increased in severity, the sole request which Moosaa made to the Pharaoh was that he should allow the Children of Israa’eel the freedom to leave the land of Egypt and emigrate to wherever Allaah willed that they should go, in order to save them from the torment inflicted upon them.
“So go to the Pharaoh, saying, ‘We are the Messengers sent by your Lord, to order you to free the Children of Israa’eel. So release them and cease tormenting them. Indeed we bring you a clear sign from your Lord, and peace and safety from Allaah’s punishment are for those who follow the guidance.’”[8]
It was a sublime call to the tawheed of Allaah containing light and wisdom. It was also accompanied by an eager desire for the guidance of those who were being called, and that they should be purified. It also contained a clear example of the utmost patience and forbearance in enduring great harm, and in facing tyranny and haughty oppression. It also shows the way to face the most difficult situations with wisdom and forbearance, whilst having the strongest hope in Allaah, that He will assist and grant victory to the Believers and destroy the unbelieving oppressors. Including clear lessons for those who make their call purely seeking the Face of Allaah and desire to rectify mankind and to turn to their Lord, and for them to be guided to His Straight Path.

Footnotes :

[1] Soorah al-Qasas (28):4.
[2] Soorah Taa Haa (20):9-15.
[3] Soorah an-Naazi’aat (79):17-19.
[4] Soorah Taa Haa (20):43-44.
[5] Soorah an-Naazi’aat (79):21-25.
[6] Soorah al-A’raaf (7):127.
[7] Soorah al-A’raaf (7):128.
[8] Soorah Taa Haa (20):47.