It seems a legal issue was something that RICO fixed in 1970.
It was hard to pin down the mob boss to particular murder. They could get the lower level hitmen, sure, but tying it to the main boss was difficult. Recordings were not really a thing back then. Those that did talk were killed.
Rudy Giuliani (yes that Rudy Giuliani) had the first successful prosecution under RICO in the 1980's.
