Alright, so probably a bit of a hot take, but I’m not seeing this him trying to make excuses for being a greedy capitalist shithead, but more of a genuine mental break.
To be more specific, I think he was definitely genuine in his goal of helping the town survive and grow after the first attack, not out of greed but genuine love of the town, and all the memories he’d created there.
The second one is clearly what changed everything for him, but I still don’t think the motivation is as simple as just wealth or greed or all that for him. It doesn’t seem like his wife tried to argue with him about staying in the town after the dungeon appeared, and seems to have approved of his aim to restore the town. This is why, when the second attack led to her death, he feels that it is entirely his own fault, and that if he’d just left the first time like everyone else planned to, she would still be alive.
Instead of making the probably smartest decision however, which would be to abandon the town with his son and go somewhere safe, the absolute misery and grief from her death coupled with the knowledge that it was largely his fault in the first place broke him, which isn’t uncommon in the real world. And, like people also tend to do in similar situations in real life, he ended up trying to rationalise it, desperately searching for some sort of reason or meaning, because accepting that his wife had died a meaningless, avoidable death for no reason whatsoever would completely destroy him beyond repair. So instead, he doubled, tripled and quadrupled down, pouring everything he had into his goals in growing the town and making it better and better, so that even though his wife had died, it hadn’t been for nothing. The town genuinely was happy and thriving after all, and his warped thought process clung to that fact to show that it wasn’t the wrong choice, that the decision to stay there really had meant something in the end.
As for his son, well, despite believing he needed the dungeon to keep the town alive, I doubt he’d be all too into the idea about potentially losing his son to the dungeon that had already taken his wife, so he tries to discourage him from it by making it too difficult to get the necessary equipment, hoping it’ll eventually make him give up.
Anyway, just to be clear, not saying I agree with any of this hypothetical reasoning I’ve listed here, I’m just trying to play devils advocate and dig into what I was getting from his story and behaviour. I also don’t know if I argued the points I was trying to make particularly well, because as clear as they are in my head, they tend to get pretty messy and jumbled up when I try to put them into words. I’m hoping I at least sort of managed to convey what I was trying to though, that he’s not just your average evil rich guy only motivated by greed, but a miserable old man, broken by the guilt of his greatest mistake and desperately trying to prove to himself that it wasn’t completely meaningless.