Spencer fought for, and got KO'd in multiple organisations...
Fighters with 40+ fight careers are trying to get a payday, but you can't blame the UFC on this one.
Training has changed a lot too... "Gym Wars" also shorten/end careers... But at the end of the day, its a fighter's decision whether he wants to go back and get knocked out again after he has already started showing signs, which a lot/most of them do, starting with headaches, menory loss, and so on... Also he was cramming fights at one stage... CTE awareness was a lot different back then, and i think his own people could have protected him much better.
It sucks to see Spencer in this situation, but blaming the UFC is pointless, and he won't win a thing.