Spike was always an assistant and living in the shadows of ponies his species was mighty and greedy and even though he was a young dragon he was tired of being used by ponies the one he loved just used him and rejected his love and the person who takes care of him all of his life just uses him as a puppet, he wants to claim all of Equestria and beyond that for himself he will gain support from any pony that will help him take the throne from Celestia and the Mane 6.