CTE is a condition and it's not new though it was discovered in 2002. It's not a diagnosis, since you have to be dead to know for sure if you have it. It was found in our 70s stars since Dr. Omalu discovered CTE and lived in Pittsburgh at the time.
The Berfict hit is moot. AB had CTE with or without that concussion. He's a small player getting hit by larger players every play. In practice, preseason, and games. It adds up over time which leads to CTE. Concussions can happen to anyone, constant head trauma causes CTE. It was called 'punch drunk' in boxing in the early 1900s onward, but the condition still existed. Reduced mental aptitude and inability to control emotional outbursts leading to degenerative mental conditions like bipolar disorder, Alzheimers, and dementia.