Here to throw my hat in the ring and offer another perspective from my own experience.
I forgave a cheater in my younger years (mid-late 20s). We were together for a few years before the cheating, and then stayed together for a few years after the cheating, but eventually broke up over other things.
I think the problem was that - besides from the cheating - the man was generally a low-key twat. I didn't realise at the time, although none of my friends liked him (red flag): the cheating was just one symptom of his general twattyness.
He apologised for cheating and seemed genuinely sorry, but had 'excuses' like feeling low, depressed etc (we were in a long distance relationship and he was long-term unemployed when the cheating happened, and I found out by chance a couple of years after the cheating incident). However, those same issues of being 'low' and 'depressed' led to other twatty behaviour towards me at a later date - for example, belittling me, constant criticism, saying I was ugly etc.
I guess what I'm trying to say is, even though the cheating stopped, him being a twat continued. Ultimately, I think he cheated because he wasn't happy/ ready to be in a committed relationship... (whatever reason), and that's why I should have ended things as soon as I found out about the cheating: he wasn't that into me/committed to a monogamous relationship, and was a liar. Rather than, for example, trying to work on his issues of low mood, depression and forgiving 'a mistake'. Luckily we had no children/mortgage, so that didn't come into the equation. I did love him deeply though, and he was my world.
If you can help it and have a choice, why waste anymore time with a cheat (or a twat, abuser, fuck boy, alcoholic, sex addict, narcissistic, sociopath... whatever negative adjective) once you realise they are disfunctional. Life is too short and they will bring you down again, even if not by cheating, because they don't deal with issues like an adult. They deal with issues by [negative verb - drinking, lashing out, lying, shutting down, criticising others, blaming others etc.].
This is separate to the trust/ will he cheat again/ has he cheated before issue.