I heard Bell wanted to use enlarged UH1 fuselage with the 139 powertrain and dynamics, or put a two bladed tethering rotor head on the 139 fuselage
HaHa!
But seriously . . .
I don't think Bell sold it's stake, it was more like the Italians realized it was going to be a big success, they did most of the R&D, manufacturing, and incorporated the technology, and they didn't need Bell to market the aircraft in the U.S. so they simply let them go.
Think about it, with or without Bell the aircraft was certified, and operational close to the specified dates, and what has happened with "new" Bell aircraft in the recent years, they are always delayed, and when they do come out, they are not what was advertised (427), or like the 407 which although now is a great aircraft, at the beginning it had millon expensive ASB's.