I think in the case of LoPresti at least, that his involvement with the Montagna side was moreso for revenge over what happened to his father, years earlier, as opposed to having an actual gripe about kicking up to the Rizzuto group and those involved.

On a sidenote, here's a photo of Paul Sorvino & Anthony LaPaglia as Nicolo Sr & Vito Rizzuto from the upcoming miniseries, Bad Blood.