I don't know, I don't really buy that this all went downhill with Trump. It's easy to say that about someone you don't like and fail to overlook all the signs with someone you like.
It was clear he was unfit to be a president, but he was mostly golfing.
We call this confirmation bias.
I doubt any president would really be able to golf for much of his time. Though you can believe what you'd like. I would love to find evidence for this belief though, where do I Look?