وَكَذَٰلِكَ مَكَّنَّا لِيُوسُفَ فِى ٱلْأَرْضِ يَتَبَوَّأُ مِنْهَا حَيْثُ يَشَآءُ ۚ نُصِيبُ بِرَحْمَتِنَا مَن نَّشَآءُ ۖ وَلَا نُضِيعُ أَجْرَ ٱلْمُحْسِنِينَ

‘Place in my charge the storehouses of the land.’ (The original Arabic word translated here as storehouses [or granaries] literally means ‘treasure’). Seeing that he had the attention of the king, Joseph made this request to him, so that with the help of government resources he should be empowered to construct large granaries throughout the whole country, where surplus corn acquired from the farmers and could be stored for the first seven years. The king agreed to this and, exercising his constitutional royal authority, gave Joseph all kinds of power to facilitate this task. The king of Egypt was a polytheist. Verse 76 shows that after the appointment of Joseph the religion of the same king prevailed in Egypt for about ten years. This tradition of the Prophet of God shows that acceptance of a subordinate post under a non-Muslim government is not against Islam. On the same basis our predecessors accepted the posts of ‘Qazi’ under tyrant kings. (Tafsir an-Nasafi). What was Joseph’s purpose in assuming authority in Egypt? The information given in the Quran indicates that his purpose seems to have been to save the subjects of God from famine and then, as a result of this, to create opportunities for the Children of Israel to settle in Egypt.

— Source: Tazkirul Quran (Maulana Wahiduddin Khan) via Quran.com (12:56)