TB, I think you're right about people trusting Vito's judgement. Also, the novel makes the point that Vito's relationships with people were quite personal.

But I've never understood what it was about the drug deal that Sonny found attractive as he expressed it. The Corleone part in it would be political and legal protection. Such protection would be rather passive. Thus, it would not be an operation such as Sonny was seeking.

"Generosity. That was my first mistake."
"Experience must be our only guide; reason may mislead us."
"Instagram is Twitter for people who can't read."