I promise this is not relating to a personal experience, just from conversations with friends who have either cheated or whose partners have had affairs.
We're always telling people that they should leave their significant others before having any sort of connection with another person, including what is now termed 'emotional affairs.' Most people I know who have cheated weren't looking to cheat and only doubted their relationship when they met the other person. Therefore the timeline must be:
1.) meet someone
2.) feel a connection
3.) quickly leave dw/dh
4.) ask other person if they're interested
5.) get rejected and have nothing/ have affair
I don't see how people are expected to not commence some sort of 'pre-affair' before leaving their husband/wife. My friend whose dh left her recently said that she was horrified he hadn't tried to make it work with her after he realised that he had feelings for OW. By then surely it's too late?
I don't think people who cheat are terrible people as no one can predict who you're going to meet and how you would feel if you found a strong connection with someone else whilst you're in a serious relationship.