Sounds like a stash of stolen goods to me. And that's actually a practical reason for going there. OTOH religion wants to be accessible to the people. They build temples and such to draw people in, not make them crawl into a deep scary hole where they have a pile of random stuff.

Some religions are about secrets, not persuasion.

Mithraism was a popular underground (literally) religion among the Roman army. And the Hebrews weren’t about letting people traipse through the holy of holies.

I agree that religion is probably overused in these explanations, but it’s plausible.

Folks hide valuables too - for fear of their being stolen. And rituals often have special places for the initiated, excluding the public. So not a slam-dunk that's its stolen stuff.

The article mentions incense too.