The 27 club is just coincidence. There is also a substantial 28 club, and a notable 26 club. I'll bet the 80 club is recruiting too.
I don't know what you were doing at 27, but for me, the warranty was off and I was ready for at least new brakes. I'd roasted mine by that point. It just seems a period in a lot of lives when we hit a wall, and either adapt or go extinct. When you throw in the drug and booze scene that musicians on the road can get lost in, it's a logical time for things to snap.
I saw a list once of the 33 club, and it was a big one. But rock musicians have a life expectancy in the low 40s. They're the killifish of the arts.