That's not entirely the individual's fault. With many (or most) academic fields, leaving academia for industry is seen as failing, and leaving the institution means leaving the network.
It’s definitely partially academia that does this. When you are a grad student you are paid so poorly and worked so hard it is difficult to build a substantial identity outside of being an academic. Academia is good at marketing itself as a noble cause that imbues very high status if you can ever “make it” so quiting is giving up on that lofty dream. Where in industry it is definitely “not cool” if you build your identity around your job. That creates a helpful firewall that pushes people to develop something outside their work.
This is very true. The only way I coped with it was by basically just cutting off any contact I had with people in my former field, with the exception of a couple of friends. Or at least, I like to think that I cut off contact. A more realistic assessment is that I simply ceased to exist to most of those people as soon as I left the field.
I did the same thing. It wasn’t conscious, it was more that they lived in a completely different world from where I went. We couldn’t really relate as much anymore. Like we now had very different approaches to life. Academy moves so slow. When I check up on people I’m just shocked at how little has changed with them.