Another possibility lies in that some drug use can damage arteries because of scarring, which then makes them brittle and open to splitting, which leads to aortic dissection. I am not saying Fletcher was a druggie, I don't know him, but 'rare' medical events of this sort have causal factors, they don't just happen. However, vax-induced damage to vascular system is happening, and I'd suspect it was indeed vax or boosters adding up.