He's very very much not the source of this. It's been ascendant literally my whole life, my first foray into really thinking about politics was trying to convince my friends that humans caused climate change and there wasn't a conspiracy of climate scientists trying to trick them so they can get more grant money.

You can see him pretty clearly expanding on and exploiting those existing currents though. One of the ways he got big in American politics is his support of the "birther" movement where he was convinced Obama wasn't born in the US (which, to be clear, was a ridiculous claim and especially galling to me since my birth certificate is from the same hospital and looks almost exactly like his). His political persona gas always been tied to the idea this idea that people are lying and working against America even if he didn't originate the idea.

Edit: also tone is hard to parse on the internet so I'll clarify that this isn't really meant as an argument, it doesn't seem like we really disagree on what Trump's politics is about (even if we have different opinions on those politics). I mainly just wanted to clarify that I saw this long before Trump, even if he's now emblematic of it.