The news media protected FDR and his wheelchair for all his terms. even the cartoonists of the time showed him up and walking. He had polio.
Many members of WH Press Corps were fully aware of Kennedy’s prescription drug issues as well as his non-stop womanizing...and said nothing, not even after he left office.
But, the FDR problem you highlight is even more remarkable. That they would refuse to report FDR’s use of a wheelchair is terrifying. Even today, you rarely hear that factoid discussed by members of the mainstream media. I bet a significant percentage of Americans know today FDR wasn’t ambulatory (if they know the name at all).
So, he wasn’t mentally incapacitated .