"Follow the money" is always the best bet in Mobdom, In one account I read years ago, Profaci reputedly promised the Gallos some or all of Shots's territories as a reward for killing him. They did it, but Profaci welshed. Had Profaci done what he promised, the Gallos probably wouldn't have gone to war. But he didn't. The Gallos kidnapped Joe Magliocco, Profaci's underboss, and some capo, and held them hostage. Profaci had to call a Commission meeting to resolve it. The Commission ordered the Gallos to release the hostages, and Profaci to give them the promised territories. Again they complied, again Profaci didn't. That's when the Gallos went to the mattresses, and that resulted in older brother Larry being nearly killed by garrote in the Sahara Lounge--saved when a cop happened in. (This was the basis of the Frank Pentangeli/Rosato brothers scene in Godfather II.)