“Something happened; he went from vigorous, dashing and (relatively) sane and benevolent ruler to a deadly tyrant, supposedly in a short period of time.”
During the last year or so of his marriage with Anne, Henry got into a major accident at a joust that rendered him completely unconscious for hours on end, literally comatose. He woke up, got better, and then seemed to go on a rampage, killing his wife and members of her fmaily and friends. Add in the NEED for a son to succeed him and he then went off the rails.
It could have been physical, but I always thought it could have been pure mental also.
I’ve never known anyone to wake up from a coma without any change in their thought processes in some way or another. But it could have simply been the fear of God put in the man - at that time, a king had to be physically vigorous. It was still a time when kings fought on the battlefield.
He could have waken up, and said, geez, I’d better have a strong son or Spain is going to own my country.