The Boosting Incident happened back when the first wave of superpowers appeared on Earth. Of course, not anyone wished to be a superhero even before the superpowers surfaced, but that's not the only point why villains appeared in the world.
The establishment of a new order, of an invisible hierarchy, occurred in an instant, leaving those with and without superpowers to fend for themselves while lawlessness spread throughout the land. There were no rules regarding humans with superpowers so the government couldn't do anything about it. The least they could do is rewrite some laws and alter human rights as the governments see fit. Needless to say, there was chaos, and for a brief moment, it's as if the world is plunging directly into another world war.