I will bet that the crappies will indeed eat dying small tilapia. When we had the thread fin shad die offs in late fall in Kansas, the shad would twirl and spin. The crappies, walleyes and even channel cats would all stuff themselves to the point of distended bellies! :-)
Yes, threadfins were stocked in spring in locations where they died overwinter. The first spawn from those stocked threadfins would actually mature by late summer and spawn themselves. That late spawn is what produced the large amount of prey, and those small threadfins late in the year helped small predators like that year's year class of LMB and the adult crappies.
