Why did the ancient egytians mummify people?

The ancient Egyptians believed that when someone died, their soul left their body. The soul would then return and be reunited with the body after it was buried. However, the soul needed to be able to find and recognize the body in order to live forever.

So they believed that the soul would leave the body and then come back after the pep is buried. But for the soul to return, it needs to recognize the body, which is why they mummified the dead bodies.