Joseph, the prime minister of Egypt had saved the people from dying of starvation and all Egyptians had experienced it and they valued highly Joseph and his God. Joseph needed permission to leave the country, however he did not go to pharaoh, first he needed the approval of all the nobles in the house of pharaoh and asked them to bring the request to Pharaoh about leaving and bury his father.
Pharaoh loved Joseph, he needed him and his God to run the country successfully and the nobles and also the people knew it, they depended on Joseph and trusted his words when he said he would return. Joseph had political power in Egypt, he ordered the physicians to embalm his father for forty days, he did not ask anyone for permission, in Egypt he had the complete power with Pharaoh’s signet ring on his finger.
Charity and wisdom
That which characterized Joseph as political leader was not the power he had, it was the trust and respect he had gained from the people, the leaders throughout all the provinces of Egypt, from all the nobles of Pharaoh and from Pharaoh himself. In addition, he had the respect from all the surrounding countries which he saved from hunger and misery when the seven barren years lasted. Joseph was well known for his charity and wisdom.
When Joseph left for Canaan thousands of people came with him, all the nobles and elders of Pharaoh, all the elders throughout the country, all the adults of the Israelite and those who belonged to their camp. With them came also a strong army for protection. They left a weaker Egypt behind, however in the times of Joseph, Egypt had no enemies, God had given them peace with their neighbors.
God saw what happened
I think the main reason for sending an army with Joseph was to protect him and lead him safely back to Pharaoh. Pharaoh needed Joseph, he meant security and wealth for the land and its people. Joseph did all this, it cost a lot of money, the journey took several months, however Joseph did it. He swore to his father to do it, but Jacob was dead, so why? The answer is faith in God, his father died, however his God lived on and saw what happened. Then Joseph and the vast company returned to Egypt as he had promised.