These things were accomplished so that we might believe. Jesus was transfigured into a partial light body and seen with the two witnesses, Elijah and Moses. He could have easily taken up the full light body and ascend to the Father but instead he also wanted to prove to us that it can be done even after death and the grave.
He wanted to prove that it can be done in life and in death.
Only the Father knows the Son and only the Son knows the Father.