I thought he was murdered years after the fact because he was on the opposing side during the war, it was simply payback / a grudge. They were tying up loose ends? Not necessarily that he was going to make any move to assume control of the organization.
Little Allie Boy was prepping to go to prison on the gun charge. Allegedly, it was assumed that Wild Bill - the titular underboss - was going to make a play for power while Allie was inside. That's why he was whacked. It wasn't just an out-of-the-blue thing.
