Agree , Marcello probably had a role but not a big one

Ask yourself who has the power to turn off the FBI security watch list

Not too mention the guy that stood directly behind upon his attempt to enter Mexico was a CIA agent ( can't remember name off top of my head )

Then to mention the hundreds of cables going back and forth between MC and Langley after it was discovered LHO was impersonated and this was while he was in MC - OCT . It appears from the docs released the CIA was trying to find out who was impersonating him not realizing this huge paper trail would lead to the ultimate blackmail / cover up.

Marcello and the mob were powerful and some worked with the CIA but no way did they have this kind of power , only people deep in intelligence can do this stuff.