Its just my theory, but having fished Kaw lake since it was impounded in 1976, I have a feel for why its on fire now, and has been for the last 3 years.
Its water levels during spawning season.
Since Kaw is the first dam on the Arkansas River, it takes the brunt of the runoff from The snow melt in Colorado, rain in Kansas and Northern Ok., buffering the water fluctuations for the down stream lakes.
I can't remember a single spring that the lake levels didn't go up during the spawn 10-20 feet at times, only to be drawn down a foot a day depending on how many gates are open.
Since the drought started 5 years ago, water levels have remained stable during the spawn. Not only crappie but bass which need real stable water levels to spawn have benefitted. Bass tourneys back 10 years ago were won with two or three fish weighing a max of 3 lbs. Now they are catching limits of 5 fish with 20# stringer weights at times.
For years, we never caught small crappie. Just about everything was a slab. Now with the stable water levels, 4-6" crappie are being caught in big numbers.

So, using those anecdotal observations, that is why I think Kaw is loaded with crappie, and just getting better.