I think in this case especially, its the betrayal aspect that makes it so much worse. Cheating is awful but it happens, in lots of marriages for lots of reasons. But she cheated with the guy who was counseling him for depression and anxiety - I cannot imagine how it would feel to know, going through a breakup and divorce, that the person I told all of my most difficult secrets to and trusted with my fears was using them against me, sleeping with my wife, imaging them in bed laughing about it, or feeling pity. Probably the two people he trusted most in the world and they utterly betrayed him. If it were me I would want to kill them both, quite literally.
Compound that with the fact that he was the only breadwinner and earned significant money, while she dabbled in vanity careers that probably lost them a fortune, and now she wants more than half their earnings (plus child support which will be significant) - it's not really sexism, she's just a straight up villain. And the "pastor" is 10x worse.