Later, he will say it was a calculated choice, that he looked at the odds and looked at the clones and decided that better the Jedi he didn't know than the Sith he did. This is, as it happens, a bare faced lie. (or: A Sith Lord realises, abruptly and rather late, that war means casualties, and decides that the great Jedi genocide plan can go fuck itself.)

Every single school had one: someone at the top of the food chain. An acme. Someone who could do things under a teacher's nose, escape consequences, and terrify other people. Someone who looked down on everyone else like they were prey. An apex predator. And Izuku couldn't count on teachers and adults to protect anyone. Even a hero school wasn't safe from the phenomena. When Izuku gets to Yuuei, he's determined to find out who it is and ensure they can't hurt him or his new friends. ...and accidentally, in the process, becomes the apex predator (though he is mostly unaware of this, and uses it for good. But still, people are terrified of him.) (Or, a snowball chain of events wherein Izuku's paranoia leads to 1A becoming a family, everyone in school being in debt to him, Aizawa adopting everyone in his sight and slowly growing closer to committing acts of arson, the League gaining redemption and working with the resident Apex Predator to combat the Hero Commission whilst gaining technically legal identities, and Hawks finding a family. Hurt people help other hurt people, and they're all doing their best. Some laws may or may not be broken in the process.)