I’ve heard it said (by a sociologist) that unwinding conspiratorial thinking requires approaching someone with compassion. Rather than tell them that they are wrong, ask them to explain why they think a particular thing.
Honestly, I don’t have the patience or compassion to try to do this. I gave up trying to talk my mother out of her Fox News beliefs and instituted a “no politics” rule in our relationship in order to save it. Best move that was available for me.