To be clear, your logic here is on Russian trolls is: There are no people hiding because I rarely see them any more.

As in they've lost their motive to hide which seems pretty implausible. Or the alternative would be you don't see them easily because after years of practice hiding they've gotten better at it. The latter seems more likely.

I'm just wondering, how do you spot these agents? For me, even though I know there's astroturfing going on, I can never spot them.

See e.g. https://old.reddit.com/r/IntelligenceNews/