He was incredibly tall.
He was whacked apparently because he was summoned to a meeting with boss Rusty Rastelli.
Rusty said something that Bonventre didnt like and so he (Bonventre) got up and walked out.
You CANNOT dis-respect a boss like that and expect to live.
Bonventre seemed an arrogant son of a bitch.

He was also a capo who had the honour of having Tony Mirra under him.
I wonder what Mirra's reaction was when he learned he had to answer to a kid half his age?