Yeah it's usually it's the other way around, troll farm gets knocked of bigger sites they increase activity on smaller sites.

Though it is possible they may have been disrupted by another actor using capabilities beyond what Facebook has once it was identified. Or maybe they were active on both Facebook and Lemmy, but after Facebook shut them down, it wasn't worth keeping it going just for smaller communities like Lemmy.

Or maybe it's just a coincidence. Who knows?