Most "youtube Leftists" fall into either the hardcore camp (this would become breadtube back in the day) or the "pretending to be logical/factual" camp that is designed to manipulate you into Leftism through slow mindvirus. Where they keep softselling you things that are "objective fact" and then build up to a point where you can't reasonably disagree with their Leftie conclusion because you agreed the whole way there.

Those types usually flavor themselves in some specific niche as the initial bait. Atheism was the classic back in the early days, and SFO obviously used anime (another very common one).