Manipulation is Key~

Izuku never got OFA and is actually in the league of villains. He has a powerful quirk too.
Him and Katsuki never met btw.
Although every one thinks that Izuku works for Shigaraki, including Shigaraki, Izuku is actually the one pulling all of the strings.
While Shiggy thinks that he is in control, it's actually Izuku manipulating him into thinking like that. Izuku has always been the one in charge. From the beginning when he "hinted" at the idea of making the League and let Shigaraki think that it was his idea.
Soon though, Izuku is going to show Shigaraki his place. And if he doesn't comply with it, then Izuku, or rather Glitch, will simply have to deal with him.
He knows that AFO won't do anything about it. After all, AFO is the one that said that he could do whatever he wished when it came to the League and his goals.