I think it's just a self esteem thing, as others have said.
My ex was an actor and once in a TV soap (about 10 years before I knew him) and I only ever find myself mentioning it online. Even my youngest kids didn't know their dad was in that soap they happen to watch, until one of them had to pretend to be a character in something similar, in drama. In other words: they were at high school before I even mentioned it. He was a prat and I left him when the older child was one and the younger child a pregnancy. I never talk about it with anyone IRL, only online. My self worth isn't located in what I was 15 years ago. But for many people, it maybe is, and understandably so.
All that said, we all have a bit of 'the grass is greener', and sometimes daydream even if very happy now what it might have been like if we'd stayed with an ex, don't we? I have two exes I often wonder about. He isn't one of them. I feel he was my 'lucky escape' and for all you know, that's how your wife feels too? Even if he is a 'grass is greener' ex, he sounds firmly in the past.
My actor ex had a famous ex of his own. He was always harping on about her. She sounded like a dick, I thought at the time but now I just think she is probably, like me, congratulating herself on her lucky escape, too.
I'd forget it. It's no more important than if he worked at Tescos.