There's a Bizzaro World 'tism to the conspiracy types.
Ever see someone who puts THOUSAND of hours into a train set or Minecraft world, etc that almost NO ONE fully appreciates it on their level? but just a SINGLE person take more than 30 seconds to appreciate it that that compliment lasts them a lifetime.
Same goes for flat earthers, 9/11 inside job, Big Foot hunters, and so on.
Feigning interest is likely the biggest slight you can ever give to them.
"no, yeah, dude, that's tooootally interesting. Please tell me more."
(flat tone showing no excitement, remember, it's the emotion that feeds them)
First round take a few minutes to penetrate those skulls, but after that, they catch on quick.