I think it just comes down to the Christy Tick, Casso and Amuso crew being big money makers and proven killers. Around the mid 80s they had the bypass gang, painting, serious amounts of drugs, the gasoline tax scam plus the remnants of the Demeo crew. And that's just what we know of.
Gaspipe had a good, or at least a working relationship with DeCicco, Gravano, Gotti and the Persicos. He was considered such a force that DeCicco sought his "approval" when they were making the move on Castellano.
So even though he wasn't part of the Bronx faction, I'm sure Gaspipe seems like a legit choice of successor in Tony Ducks mind around 1986. He probably couldn't have predicted how nuts Casso was/became.
