The bomber mistook DeCicco for Gotti as they looked somewhat similar from afar.
The Gambino’ s owned ( still do ) the DeCalvacante’s.
The Lucchese’s were very busy killing each other which would of made it very convenient for the Gambino’s to clip a bunch of Lucchese guys and blame it on their internal friction which there was a lot of. Not only was it a bronx bs brooklyn thing, the jersey faction of the lucchese’s were laying very low due to Casso wanting all of them killed.
I dont think Gotti would of went after anyone on the west side as they had plenty of joint business ventures. Chin wasnt a go to war kind of guy anyway. the west side are not gunslingers anyway, they clip people much less frequently than any other family, although their murders are very public when they occur. They send messages. They dont kill for no reason and their is much less internal friction with the Genovese, hence their perpetual stability.