This is what sucks about so many people: they think others have to go through what they did — so what if you went through that ass-kissing and beatings and he didn't? A truly strong person will be better than the trauma they went through, not stoop down to its level
Though, I guess if it wasn't this Watanabe asshole — it would've been somebody else, in a different place, at a different time — the younger, cockier Izawa would've eventually been put in his place at some point; it was something he had to go through, even if it was unpleasant
Thanks to that awful experience, he's who he is now