Content that gets an extreme emotional reaction is strictly better at causing engagement, that's just like a basic sociological thing.
The result is that youtube pretty much constantly tries to radicalize everyone. It doesn't care if you get radicalized left or right, it cares that you go into rabbit holes that make you angry or emotional and have a reaction. I watched youtube attempt to do this to me, as I watched a singular video by a more radical than average leftist youtuber, and youtube immediately started recommending me the classic "angry incel right wing" content that so many young men are deeply entrenched in, but I have never been recommended in my 15 year old youtube account. Depending on your beliefs or research I'm not aware of, right wing radicalization might be more effective, as "it's not your fault, we just have to hurt and remove certain people" is more palatable to certain people than "the system is fucked and we have to gut it and work hard to build it back". In that case, it would naturally push right wing radicalization over left wing radicalization.
None of this has to be purposeful. However, willfully ignoring this outcome because it makes you a lot of money is actively evil in my opinion.
Sometimes I watch a rightwing video, and then all I get is more and more extreme rightwing videos suggested.
Then I have to watch some leftwing video to get back to more balanced content :D... but there seems to be plenty of content on both sides, with suggestions leaning heavily on which side you watched the most.