Hello from another former BW whos wxh had multiple OW. There were three I had proof of in the final year of the marriage. There are some I didn't have proof and even some craigslist ads for hooking up with men. I just wanted to say you are not alone.
The 'why' part of all of this is part of the grieving process in my opinion. You may just want to make sense of it all because it is all disgusting and hard to grasp why he would behave like that.
Eventually you get to a point where you have enough. I may never know the whole truth but I had *enough*.
To me one OW might be a mistake and something we could have worked through if he were genuinely remorseful. While it is possible for a serial offender to change, it is just really unlikely that he or she would change. That was my *enough*.
Ok, I see you have been on here awhile so maybe my explanation doesn't apply. If you're asking why he is going on a lot of dates since the divorce from a long term marriage, who knows. Do yourself a favor and stop following him stop the checking, and this will help you stop caring. Put that effort into improving yourself. He no longer matters. Side point if he's not married or in a committed relationship and these women are also single and everyone is of legal age it's no one's business.
I did feel replaced and couldn't understand after that long term marriage how wxh could just be like a trapeze performer from long term marriage right into another one. That was puzzling! but now feel indifferent about it.