The Thrilla in Manila was a special one. They had to air it at 10 AM for it to be shown at night in the US. After turning the lights on, it was over 120 degrees and 100% humidity and both fighters were exhausted by the 1st round. Both fighters also lost over 5 pounds during the bout and at the end of the 14th, Ali asked his trainer to cut off his gloves, he was done. But unbeknownst to his corner the ref had seen enough and called the fight since Frazier had taken so much damage and was so exhausted. It was a golden age for the sweet science, and I doubt the sport will ever rise to the prominence it had then.
Nothing good happens fast in an ecosystem.