Yeah but the bikers took Woolley in way before the Rizuttos did despite being "hardcore white", so what's the difference?

Again, the Rizzutos needed muscle to fight against their enemies so they took Wolley in. For whatever reason, they felt the Scoppa brothers weren't trust worthy, and later they were enemies. So I wouldn't say "they supported Woolley over one of their own". They took Woolley and Silva and whoever else they needed to survive. If there were more of "their own" on their side maybe they wouldn't have needed to.

So IMO the Rizzutos taking in non-Italians isn't the reason the mob has fallen in Canada, it's the consequence.