Because Bakugo is the writers pet character, and he couldn’t have him lose.

The whole fight in general left a bad taste in my mouth. I mean really, Bakugo straight up attacks Deku completely unprovoked, using dangerous levels of force, all to make his own guilty conscience feel better, then he has the gall to complain to All-Might about why he didn’t get All for One. Like dude, your a terrible person, that’s why. He then only gets grounded for a few days for what amounts to a criminal offense. And of course, Deku gets grounded too despite really only defending himself.

The whole fight just felt like an excuse for the writer to show off how “cool” Bakugo is, without him having to face any consequences for being a total psycho.