My point is that it’s expected to have some mental decline by that age but I would still bet on Biden if they went toe to toe on jeopardy or at a bars trivia night. And while Biden wouldn’t have been my first choice for president to begin with, he is still light years better than trump ever was even at this point and I’ll take Biden over most of the current choices on the left especially because those others have zero chance of winning.
With and without the help of things like heavy drinking, drug use, lifestyle, etc, everyone ages differently. I know this from my own family and watching the world around me. Trump has been incoherent for a couple of decades now while Biden has been able to control it (for the most part).