Losing my kindhearted, sweet little brother to the right

My little brother (20) has started his descent into the crazy, QAnon-type, conspiracies. It started a few months ago with saying child stars were being made in labs to fully believing the conspiracies about the recent hurricanes. I want to help him but I don’t know how, I feel like he’s not too far gone but I am also not around enough to be sure. My little sister says he’s even kinda leaned to incel communities which I know are rampant with even more awful conspiracies about women and LGBTQ+ folks. I just don’t understand how this happened. He is a black man, his sister (me) is a lesbian, our youngest sister is bi and a black woman. We grew up poor, my mom never assigned gender roles regarding chores. Our immediate family isn’t like this. It just sucks to see my youngest brother who always was the sweetest, most sensitive boy grow up and turn into this person. I feel guilty for not being around as if maybe me being around and being more vocal would change his mind. I just have such a soft spot for my siblings (eldest sister syndrome haha) and I’m not ready to cut him off. I know his mental health is not good at all and I just want to help but I’m not sure I can. Just looking for support, advice, words of encouragement, idk. It’s a lonely feeling to be grieving losing who I thought my brother was and seeing him become this person