I just finished "In Hoffa's Shadow" by Jack Goldsmith, Chuckie's stepson. Chuckie gave him hundreds of hours of interviews before finally telling him that Tony Pro ordered the hit, with agreement from New York and Detroit. Goldsmith, a former government lawyer, got to know the FBI and Justice Dept. agents on the Hoffa case. Chuckie didn't say who carried it out, and maintains he was nowhere near Hoffa on the day he disappeared.

Goldsmith writes:

"I learned that current and former officials in the Detroit office of teh FBI and the Detroit US Attorney's Office have for two decades believe that Vito Giacalone, Anthony's brorher, was directly involved in Hoffas disappearance and was probably the perso who picked hm up at the Machus Red Fox. These officials also believe they know who murdered Hoffa. The killer was a low-level family member in 1975. someone entirely off the early investigators' radar screen. His status in the Detroit family rose almost immediattely after the disappearance, and he died in January 2019. But the government remains frustrated because its informed suspicions about this person cannot be proven."

The government botched the investigation of Hoffa's disappearance, in large part by simplistically focusing on Chuckie as the prime suspect. That was based on the equally simplistic assumption that Chuckie was the only person whom Hoffa would have felt safe enough with to get into the car that took him to his doom. They never had any proof of either premise, and wasted far too much time pursuing Chuckie, who was never indicted, much less convicted, of anything related to the Hoffa disappearance. And, they overlooked the obvious: If Chuckie was with Hoffa, and/or knew anything important about his disappearance, the Mob would have whacked him immediately.