QAnon is more than a conspiracy theory - it operates more like a cult, except that Trump, as figurehead, has been chosen by the members as a stand in for a charismatic leader. And those who fall into its trap aren't gullible weaklings - a lot of them are intelligent, otherwise good people which makes it even more tragic and hard for us outsiders to understand why falling under its spell happens. I have a friend who fell down the rabbit hole and she went from someone who used to poke gentle fun at Trump to someone who near worships him.

Other factors that might make people fall for QAnon are significant life stressors and suffering from current world events, all which my friend and her partner have endured. I think the advice you've given here is very good, as in, when they bring that stuff up, gently let them know you'd rather not discuss it. Trying logical arguments against their theories doesn't work - cult-speak (e.g. calling legitimate information sources "fake news" and telling you to "wake up") takes over at that point. If you're not wanting to cut that person out of your life, drawing some pretty tight boundaries is the way to go.