Because they think it's a stupid proxy war that doesn't serve the US (because it strengthens BRICS which hurts the Petro Dollar) and that US support for Ukraine is a ploy to ensure that supposed US funded biolabs (that are pretty much confirmed to exist, afaik) aren't uncovered, because Joe and Hunter Biden are likely to be involved in them via the company Metabiota.
I'm as irritated as everyone else because it's usually not the Republicans to be the sane ones but it seems the Democrats are even more corrupt nowadays. The FBI is actively trying to suppress evidence of bribery of a sitting President and it's even denying answering Congress (or Senate? Not 100% sure which one, I'm not an American) inquiries.
The world has gone mad.