I never went further right than voting democrat, but I used 4chan occasionally for a good decade and I’m convinced that support of Trump’s campaign on there was well-understood to be a running joke until people unaware it was a joke started joining to participate. I’ll admit I wasn’t using it much anymore at all by that time, but when I saw comments about Trump support start popping up the first couple months my thought was “this is hilarious”. The idea of actual Trump supporters existing was not something I was capable of imagining at that time.