OK, the killings of black people did happen, and just over 100 years ago. It was part of a larger more-or-less nationwide reaction by some racist whites against black men who had returned from service in WW1. The racists were "afraid" blacks would be emboldened to get "uppity" or some such racist silliness. But the lawsuit was not about people specifically injured by the killings or specific damage they had suffered:
The lawsuit was brought under Oklahoma’s public nuisance law, saying the actions of the white mob that killed hundreds of Black residents and destroyed what had been the nation’s most prosperous Black business district continue to affect the city today.
It contended that Tulsa’s long history of racial division and tension stemmed from the massacre, during which an angry white mob descended on a 35-block area, looting, killing and burning it to the ground.
Beyond those killed, thousands more were left homeless and living in a hastily constructed internment camp.
The city and insurance companies never compensated victims for their losses, and the massacre ultimately resulted in racial and economic disparities that still exist today, the lawsuit argued.
It sought a detailed accounting of the property and wealth lost or stolen in the massacre, the construction of a hospital in north Tulsa and the creation of a victims compensation fund, among other things.
My emphasis. US Tort law, dating back a millennium or so, is based on English Common Law. The one(s) suing must prove they have been damaged, prove what their economic damages were, and awards are limited to those economic damages (in some cases with some punitive damages, punishing the specific person(s)/entity that did damage). This lawsuit was a fishing expedition, by people using the few centenarians as proxies, seeking awards far beyond and unrelated to real damage done by the race-riot and killings.
Put it this way, if this non-lawyer whose "legal education" is just a Business Law 101 class taken some 40 years ago can see the gaping holes in this case ...