It's a much more enjoyable NTR game when the MC isn't such a pathetic character and actually reacts like a human when learning of their cheating partner.
I've come across this notion in discussions and people often reply that no, they don't want the MC to win her back, she cheated, she's done, any "winning back" or forgiveness is a further sign of weakness. It's mind boggling how that running away isn't seen as weakness itself. Then, people talk about NTR as a consequence, that it needs a trigger - hence the flawed MC, however those flaws manifest. I think it's all bullshit, bad writers (but, most of the time, bad commenters) talking about putting together a story using common tropes and binary logic, because they lack the imagination for coming up with something original.
But I don't play NTR; so, what would I know? I can't understand the appeal of experiencing the "feeling of betrayal or loss" (sorry to borrow your own words), or the dread of suspecting it's happening. And I really don't like when NTS games include that, sometimes justified as in order to allow for branching out to NTR. An underconfident MC is already akin to NTR, as I tried to put it, regardless of whether he gets his LI stolen, or accepts to be a cuckold passenger in her (or the bull's) power trip. It's all masochism (or sadism, if the player identifies rather with the LI, or the bull, and enjoys the story from a bully's perspective).
But I do agree with you that it might be ok if the MC reacted differently - NTR might work for me, but I'm only up for a very narrow scope of MC reactions. It has to be a MC so confident they never even worry that the outcome of cheating could be his loss or defeat. Cruel or violent revenge don't appeal to me. He'd play things with cool confidence, so that in the end, his LI would come to despise the bull - not really NTR, in fact, which is why it never happens. You might say this would be a superhuman MC, and I'd argue that I prefer some fantasy and heroism in my characters than predictability, the pretence of realism or the affirmation of socially accepted tropes.