Why were bodies of pharaohs and other important people preserved as mummies? Why were they then put into pyramids?

Because Egyptians believed that this life is just one phase that lead to the one that starts after we die. That is why pharaohs and important persons were  mummified so their body would be preserved to continue the road. They were put in pyramids, because they were built to be their tombs.

Explanation:

Process of mummification was a complex process which usually lasted for 17 days. Everything had to be well-planned and people who were involved in this process were to be very careful. Pyramids that were built as burial places actually presented greatness and importance of pharaoh that was to be buried in them.