I always thought that it was because Satan wanted to be like God… in that he was selfish, as shown in Isaiah 14:12-17…
"How art thou fallen from heaven, O Lucifer, who didst rise in the morning? how art thou fallen to the earth, that didst wound the nations?
And thou saidst in thy heart: I will ascend into heaven, I will exalt my throne above the stars of God, I will sit in the mountain of the covenant, in the sides of the north.
I will ascend above the height of the clouds, I will be like the most High.
But yet thou shalt be brought down to hell, into the depth of the pit.
They that shall see thee, shall turn toward thee, and behold thee. Is this the man that troubled the earth, that shook kingdoms,
That made the world a wilderness, and destroyed the cities thereof, that opened not the prison to his prisoners?"
As the bible crosses between all time, from past, present, and future, I also believe that Paul was inspired when he wrote about the battle of St. Michael and Satan (Revelations 12:7-9).
As to when, I wouldn’t know. It seems to be all speculation from there.