I spent quite a bit of time exploring this topic some years back and have engaged with all of the nuances you have elaborated. However I still think you can reduce this part about the 'little primate brain that just wants to fuck' to a moral decision where the cheater is simply willing to put their own needs over those of everyone around them. The fact remains that maaany people _can_ ignore this part of their brain and after all the books and articles, I still feel they those who can't are just wimps when it comes down to it.

We have words for people who are not willing to sustain pain for a greater good and we have words for those who can.

Alain de Botton's book was the worst. It attempted to glorify it as being some necessary/indirectly selfless act done for the preservation of a marriage. Deluded