When God gave the angels and humans free will he took the chance some would chose the wrong way.
That is what happened. The devil wanted to be worshipped.
Genesis 6 chaper tells how these other angels came down and lived with women. Jude 6 before the flood.
They too wanted to be worshipped. They were the mighty ones of old the men of fame. So because they were not human did many powerful works. Angels are mighty in power.
So they people began to worship them.
Apparently it was still going on in Jesus day because Satan showed him all the kingdoms of the world and said he would give them to him. Can't give something you don't own.
Jesus never said he didn't own it. So the Bible says Satan is the ruler of this world. Those other demons live here to Rev. 12
speaks of a war in heaven and Satan and the demons are cast down to the earth. They are worshiped as gods or prophets or mystic leaders and do horrible things to people.
Would a religion that tells a young man to strap on a bomb and blow people up be from a true loving god. Kill people you don't even know. So the demons are in religion worshipped as God's.
Jesus said, Test it by its fruits, if it isn't publishing peace and love and forgiveness. Christian or other wise, it isn't from the true god.