I'm thinking the difference is more in raw numbers. Bernie's army is nearly the same size as Hillary's. Cruz's army was maybe 20-30% the size of Trump's army, at its peak. I think Hillary and Bernie are probably closer personal friends than Trump and Cruz will ever be, and I am sure there are plenty of Cruz supporters who are genuinely #NeverTrump.
I think Donald has more true love, which ameliorates the effect of the enmity. He will defend against pot shots from Cruz, but absent that, has no real reason to expend energy mowing Cruz down.
Having actual support split between Bernie and Hillary, though, looks like it bodes to hobble the Donks but good. We won’t even see faces; we’ll see nothing but slung mud.