The more popular a library is, the more support its ecosystem gets, and the more likely you can convince your boss/company to use it. So if you prefer one, you may really want it to be "the most popular" to ensure you can keep using it.
Eg: people who really like Angular 2+ are kind of struggling right now. If you join a company and they're not already using Angular 2+, good freagin luck. Chances are they won't switch from React/Vue/whatever to it anytime soon.
Because of this, and the general perceived volatility of the JS ecosystem, its not too surprising people treat this as a "war". It's unfortunate.