I also said I knew two guys who left the regionals for single pilot freight and were dead within a year. I used this to point out that I'm not interested in that kind of flying.
I flew single pilot night freight for a couple years and have kept in touch with a bunch of my old flying buddies. The only one I know who is dead now was killed in a business jet two weeks after leaving the 135 gig. It happens in all corners of aviation. You seem to have had a stretch of bad luck with your friends and that is a shame, but it is still rare.