There was nothing wrong with this. It's actually a great way to start a series and many shounens have pulled it off very well. The abrasive asshole/bully is found in a shitty situation and the friendly protagonists chooses to save him/her. It's a good representation of the qualities of a hero, saving your enemy.
The thing is the saved character usually becomes, you know, less of an abrasive asshole even if they're still grumpy and aloof. That's another good message, that people can change. For stuff going on right now, just look at Okuyasu from JoJo. Really, it's something that happens in all shounen to varying degrees (and obviously to varying levels of success). It doesn't have to be an immediate change, but there's usually something that endears us to said character afterwards. What has endeared us to Bakugou since being saved? He doesn't outright attack Deku anymore except when he's provoked (or what he perceives as provoked)? Yeah, great character growth you got there!
I was actually really engrossed when I read the first chapter. "Man, that guy did some pretty shitty things and it might be tough for Midoriya to forgive him, but now they'll be total bros and there's no telling what they can accomplish when they work together!" It was a similar setup to a lot of my favorite series and I was excited to see where it went. If only...
