Nicodemo wasn't the shooter on the hit--he was driving the getaway car, which even the Feds admit. The shooter hopped out of Nicodemo's Honda and blasted DiPietro, then hopped back in--all in broad daylight. Most people in SP would just look the other way, but there was a postman right there who described the shooter as "short and stocky."

Now, pretty much everybody assumes that it was Baby Dom Grande (including the feds), but they can't make a case if Nicodemo won't rat--Nicodemo was caught with the gun in his car, and no one else can ID Grande. So basically Nicodemo must know that Grande and others will take care of his wife and kid while he's away (and also watch his business interests--guy was pretty successful in the legit world), because even as a guy doing 25 years, he has the ultimate card to play--he can take down the whole family if he flips.

I think the Philly FBI office also suspects Nicodemo was in on the Johnny Gongs hit, and he was also Merlino's driver at one point. He knows a lot.