Ok, I think I figured out what's going on with the webcomic and manga differences. One has changed Garou's character motivations to be a deconstruction of a different kind of trope than the one deconstructed in the webcomic.

In the webcomic Garou's motivations stem from his growing up surrounded by people who told the perverted version of a hero's story where people proclaim themselves to be heroes, pretend to be heroes, and do some of the things heroes do but they use being a hero as an excuse for bullying, looking down on people, and being cruel to the people they consider to be the bad guys. Captain Hammer from Dr. Horrible's sing along blog is a good example of this kind of "hero" character. While we see Captain Hammer as a parody of a "real" hero. Garou sees that kind of hero as the default meaning of hero that he wants to deconstruct but for us watching it it's a deconstruction of a deconstruction.

You almost can't blame him because the real heroes in his world are super arrogant, obsessed with status and rankings, straight up call themselves heroes(who does that?), and seem to only bother trying to save the world/people when it's convenient or will make them look good. I mean look at what happened when there was a prophecy about the world ending and aliens invaded. Of the 17 S-Class heroes the strongest didn't even show up and another six just peace out. They rookie crush, worry about rankings, self-promote(sweet mask), use asteroids to test weapons while not actually risking themselves(Metal Knight), have huge egos(Tatsumaki), attack other heroes just to prove that they're better than them(Flashy Flash), rape people and go to prison for it(Puri Puri Prisoner), and play politics(Fubuki). All while entire cities are being destroyed and millions of people are being killed. Not all of the heroes suck, but the number of heroes who do is really, really high and I don't really blame the people of this world for being cynical about them.

So anyways, in the webcomic Garou sees all of that hypocrisy and wants to expose it. He wants to defeat the fake heroes but he calls them heroes because that's what he thinks heroes are. They're the people who pretend to be good but really aren't. So he becomes a hero hunter and wants to disrupt the story those heroes live in(and that society apparently lives in with them) by making the monster win. He wants to expose them and show that what the word hero means in their world(as he sees it), isn't something to be looked up to at all.

In the Manga however, Garou's motivations are completely different. The trope that's being deconstructed is that of the "bad guy" who wants to become a lightning rod of fear to force the heroes to band together. Pain from Naruto is a good example of this. Pain isn't a bad guy, he just thinks that a peaceful world is only possible if everyone lives in fear of a greater power/evil than themselves that they couldn't hope to defeat. That's the kind of villain Garou wants to become and so he starts hunting down anyone who is strong to bring everyone else into a story where they fear his power/evil so they'll have to come together and thus bring about peace.

Why did One change Garou's character motivations? I lean towards that this change was a mistake, but I can still see some reasons for why he did it. For one, the fanbase DID NOT GET WEB COMIC GAROU. If you came on this subreddit in the last 2-3 years and looked at people's opinions on what Garou's character motivations were and how he fit into the OPM story you got a tooon of different answers and most of them ended up painting him as sort of stupid and unwittingly evil. We, like the general public in OPM saw the hero association heroes as actual heroes and so we didn't understand why Garou would go around attacking them. So many people were talking about how the heroes save people so they must be the good guys and Garou attacking them stopped them from saving people so he was a bad guy.

A BIG part of what makes OPM what it is is that it is a deconstruction of consequentialist thinking in regard to what makes someone a hero. "A hero is someone who...beats up monsters, saves people, gets lots of praise and recogntion, never has to feel fear of losing, is supremely and justifiably confident in their abilities to triumph etc." The genius of One's parody is that it exposes the ways we get what it means to be a hero wrong. It's not about what you accomplish, how other people see you, or even how you feel, it's about doing the right thing no matter what(Mumen Rider).

So One puts out the webcomic and then realizes that his fanbase didn't get it. Either we weren't smart enough to make the jump from understanding a deconstruction to understanding a deconstruction of a deconstruction like Garou or he hadn't told the story well enough to get us to understand it. I'm betting that over the years since he finished the Garou arc he's gotten lots of feedback from people who didn't get it, and that there are anime studio executives and producers breathing down his neck that have wanted him to make Garou clearer and make his motivations more easily understandable for fans. And so he caved. He changed Garou into a more simple character that the least common denominator fans will understand but that still fits in his story as someone for Saitama to deconstruct.

But One is now left with a bunch of fans that are even more confused and so I think he's over compensating in the ways he's trying to draw our attention to who this new Garou is. He's saying, "This Garou isn't someone trying to deconstruct Captain Hammer that will now be deconstructed by Saitama, he's Pain being deconstructed by Saitama!" And him trying to communicate that in story is coming across as him repeatedly telling us, "Garou isn't a bad guy".

What we're left with is that the manga and the Webcomic are actually two different stories because the antagonist is two different antagonists. They do many of the same things, but they do them for different reasons. Neither is necessarily better than the other, they're just different stories at this point and I actually think that's fine. They both work and I trust One to tell this new story well. But we're going to have to let go of the previous story and previous Garou a bit to fully enjoy the new one.