There is a chance there wasn’t anything incriminating. The top guys kept conversations live or intimated they wanted something done; the lowers took the planning and execution upon themselves.
Wasn't the strategy of Mafia bosses to say something vague like "I sure wish that guy would go away".
It was implicit that they wanted someone killed but if brought up in court they could say "I was just expressing an opinion, not giving an order"
Mobsters have it down to an art.
"You take care of it." means "Murder him and dump the body into a building foundation."
"I don't see any problems." can mean "The ambush will happen at the scheduled time. Vinnie will clean up the bodies."
etc.
You'll also see a lot of politicians using "dog whistle" statements, that are interpreted by listeners to mean something entirely different from the stated words.
I'm not a lawyer, but isn't RICO meant to give a way to prosecute those who are at the top of organizations that have people committing crimes like this?
Yup, i've worked long enough with senior mgmt to know that anything of interest for prosecution won't be written down, especially not on company devices. Those making the mistakes of writing things down are those actually prosecuted, the ranks and files.