> They mostly seem to be into their own thing. How can I energize engagement?

You jest, but the best way is to give the nerds only a feed and don't allow any other organizing principles for navigating the content. Lured by the promise of something interesting sometimes, people who are trying to follow their curiosity for math/archaeology will stumble into threads about corporations and products, throw ideas out in public for free, get sucked into politics, etc etc