What happened to this guy?

He's always been pretty busy, a large volume of work either in movies, television, books, plays, etc. Talk Radio was a very good movie but Bogosian played an unlikeable character - and it wasn't a commercial success. Still, even though we haven't seen much of him he's been able to make a very good living, while having a stable family life as well.

I can only ever recall seeing him in an episode of The Twilight Zone from 1985 S1E3 called Healer.

https://www.imdb.com/title/tt0734712/reference/