I know some might disagree, but I think there are some women who do set out to entice someone, especially a married man who can be blown away by such sudden attention.
I had a good friend who I extracted from my life after a few years as her catchphrase when going out was "I could have any man in this room", and she usually could cause she literally threw herself at the poor sods. She also worked her way through many of her friends husbands I had the sense to extract myself before hubby appeared on the scene. She was a damaged person, ultimately, but was dangerous and unrepentant on her actions. Shameless was the term I would apply historically.
Of course, a man of integrity should say no. But life isn't always as neat as that. If someone pursues you, it can be intoxicating. Doesn't give the man a pass, but I have seen men in long term relationships who should know better falling for this situation.
However, these relationships don't last long as this type of woman is in love with the chase, the thrill and falling in love. A few shiny money baubles also help attract them and if these don't materialise, interest wanes quite quickly.
Now, I don't know if the OW here is like that, but it does sound familiar.
Lily, I would also prepare for him trying to come back at some point, battered and bruised once the infatuation burns out. What you do if that happens is your business.
Just my experience of such situations, of course.
As I've said before, love of my life my arse. As if.