The US isn't at war in Ukraine, we're not fighting there. Nobody who's actually anti-war looks at Russia's invasion and says "oh that's fine let it happen", everyone supports the right to defend yourself.
The US is sending crazy amounts of money over there while average Americans are seeing their living standards get worse and worse. Grassroots republicans want Ukraine to fight their own war with their own money, not keep sending money over their while Americans go hungry.
So then we're not worrying about the "anti-war" position anymore, alright.
I mean, grassroots Republicans elected Reagan who beat the Soviets and Bush who wanted to "fight them over there so we don't face them here", they're certainly comfortable with spending money on the military.
They haven't historically wanted to spend that money on welfare though, so I'm not sure that Americans are going hungry because of Ukraine.