Joe Gallo was just a soldier that tried to climb the ranks but failed,he was a john gotti or a joey merlino of the 1960s.
But after his death Bob Dylan made his song Joey and in 1974 Carlo Lizzani made his movie Crazy Joey and the legend was born.
I think that Gallo was a loyal soldier that come under a greedy boss and tried to kill him but failed tried again maybe thinking that Gambino would help him but failed again and died like a man.