In the beginning God created Adam and then created Eve from Adam and when God told the Angels and the evil to Kneel (as a worship sign) to Adam, here the evil refused and said to God I am better than him I was made from fire and he is made (Adam)from clay.
God ordered to exit the evil (Sheetan)from heaven, here the evil asked God to have a chance to live till some time, and God let gave him the authority to live.
You see the God is so generous even with the evil and automatically God will be more generous with people and other living species.
When the evil knew that God will let him (the evil) live to a certain time, the evil made a challange and said to God that he will destroy or let all the people deviate and go to the bad side.
Then God said ok those who will follow you (the evil) will go to hell.
What about those who will not follow?
They should be awarded and the award is the heaven (paradis).