> I can’t understand why anyone would become emotionally invested in any of them.

I think that's simple: because they are financially invested in them. That's obvious for the developers working on the frameworks themselves or building libraries / plugins / UI-themes for them, but I believe it's also correct for "normal" developers who build things with these frameworks.

They know these frameworks and can use them, and they've made an investment in time to get to that point. Likely they're also making at least some of their money _because_ they know these frameworks. Emotional attachment follows the economic attachment, and then you'll get plenty of rationalizations.