Because many of the Egyptians believed in Reincarnation. This basically means that they believed that you were resurrected into a different but equal life form once you died. For example, If you were a calm giant when you were human, you would most likely become an ample cedar tree in the afterlife. But if you were a bold, strong, "godly-like" person when you were human, you would most likely become something "godly", such as (nonetheless) a God.