In Kentucky ...
Where I fish the most, locally ... Crappie in the 2lb range are fairly common, but not regularly caught (not by me, anyway).
In East Tenn ...
Where I fish 1-2 times a year ... Crappie in the 2lb range are common, but are sporadic catches (by me) at best.
Oddly enough, both state's State Record fishes came from small impoundments, not the larger lakes/reservoirs. KY recognizes both species (White/Black Crappie) as one, and the state record 4lb 14oz fish came from a West KY watershed lake. Tenn separates the two species, and the Black Crappie @ 4lb 4oz came from a 167ac lake, while the 5lb 1oz White Crappie came from a pond.
Any body of water that gets overpopulated will produce & maintain smaller sized fish, due in part from competition for the food source. Lack of enough predator fish or angling pressure will allow the prolific breeders (like Crappie) to overpopulate a body of water.
... cp