Maybe you can help me a bit:
What is the definition of an “isolationist” now? I knew during the Cold War it was someone that wanted the Soviets to win. During WW2 it was someone that wanted Hitler to take Great Britain. But what now? Someone that doesn’t to bomb Christian schools in Kosovo, or someone that doesn’t want to goad Russia into starting WW3? Difficult to define now, at least for me.
I think the defining characterization would be someone who is not concerned - and does not think our government, our military, our tax dollars, should be concerned with anything outside our borders. The world is a complex place, so this may manifest in any number of ways and come in any number of flavors. As for your example, I would not say it's those who wanted the USSR or Nazi Germany to win - they were those who simply didn't want the USA to be involved, period.