He was silenced because he knows too much
Being that both his parents are well known artist, I always get the sense Tracy is comfortable where he's been at for all these years. He doesn't seem like the ambitious type.
I'm sure the multiple rape allegations from different girls over the years hasn't helped. Along with his mental health and d*** problems that have him in and out of institutions and burning bridges with people. No one from GBC was able to really break into the mainstream other than Peep though. They all kinda seemed cool where they were and never really pushed for more.
Honestly don't really think he would be able to handle the fame if he got it as he's barely able to keep it together at the place he's in now so maybe it's for the best that he never got super huge. Main reason though is that his unpredictability pretty much makes him unmarketable to the mainstream and he never really showed any ambition in changing himself to get mainstream attention.