"With few exceptions, straight men will have sex with women who are willing to have sex with them in the main. If they think that that will 'only' be women of their own age, that's who they'll go for. If they think they've got a chance with someone younger, they'll go for them."
I actually had this happen to me. I am 50, divorced and just started to think about dating again. About 18 months ago I got to know a lovely guy who goes to the same running group, early 50s. I really liked him. We had great chemistry, common interests, I found him really attractive, he seemed kind etc. Similar goals in life. We were talking for a year or so, I had told him that I was still raw after my divorce, but open to taking things slowly.
We hadn't actually got to the point of "dating" when he told me that he'd got into a relationship with a woman in her 20s! I know the woman and she is very attractive. I think the guy was very flattered that she wanted him and the whole thing was based on lust. It ended within a few months and now he's crawling back to me saying that he realises "looks aren't everything" and he wants something "deeper", and he now realises what he could have had with me.
To be fair to him it does sound like he's done a lot of self reflection, but it does sting to realise that even though he and I seemed to have a deep connection, all that was overlooked when a hot twenty something made a play for him.