Why is everyone now saying the Nazis were leftists?

Because they used the word socialist.
It's the same type of arguement they use when they argue that the democrats are racist because of the positions they took prior to the civil rights movement.
Or that the civil war was faught over state's rights.
It a way for them to bend history to suit their narrative.

Mostly lack of education is my guess, but there are plenty of folks who know better and are taking advantage of the ones who don't.

Because someone random told them it's way to "own the libs."

Americans be smug and confusing online. They're anti politics - because politics is how we secure the peace and provide for the population.

Because they were?

Are you saying they were uber libertarians?