Thinking of Mahabali every Onam

During "Onam" time I have always wondered if the "Vamana Avatar" was really justified? In almost all the other Avatars of Vishnu there was one or more formidable villains or cataclysmic reasons for which the Avatar had to appear. Mahabali was in fact a Vishnu worshipper. Was Vamana eliminated just because he belonged to the Asura clan? Was he eliminated because the Gods were worried if
Bali would become a God due to his charitable and other magnanimous attributes? I am not able to find the single most convincing reason for which he was pushed to "pathala". If he were to be eliminated why be given the choice of returning to the Earth during Onam? A consolation from the Gods for the benevolent and noble person he was? Other than Karna, Mahabali is the other person whom I have always sympathized for their tragic fates.