I think we didn't see it because 1. The writing wasn't the best around this particular story arc, and 2. Most of us aren't incels. I hate to call Nate that, I really do, but as I think back over this season, it truly does describe him. Sure, Ted should'nt have have laughed at him suggesting he talk to Isaac - I cringed a bit when that happened myself, but surely Ted had built up enough goodwill equity with Nate over their time together that Nate could let that go, or at minimum grow some balls and talk to him about it like a grown-ass man. I mean, this team had its own dedicated therapist onsite for MONTHS. Nate could've sought her out at any time to help manage what obviously was becoming a ticking time-bomb of a problem, but instead, he chose to internalize every perceived slight and add it to a long list of reasons why everyone sucked and why Ted was the worst. And it's not like he was completely afraid to ask for help - he went to Keeley and Rebecca, right?
Sure, he has daddy issues and is insecure. Whatever. Maybe it helps explain the way he is, but in no way does it excuse it. We all make our own choices. Nate had an incredible support system right there, and instead of choosing to let it help him, he chose to burn down what were probably the best relationships he'd ever had in his life. He's so blinded by hubris and rage that he probably doesn't even see that.