Really? I must have missed the invite to the Biden's Liberal Laugh at Trump's Falling Down party. No matter.
I fall. I fall a lot. I'm not at the professional, Hollywood stunt man level sort of falling. I think I am approaching the 'expert' level of falling in terms of hours spent practicing.
As a young person I had a cane to help prevent falls. Then I progressed from a cane to a walker (but I don't call it a walker - it's a rollator). Currently, I am transitioning from a walker to a wheelchair. The cane lent me an air of 'distinction'. The walker/rollator is much more effective but also looks silly. The wheelchair, while most effective and safe, is just sad. At no time have any of these devices or the lack of them indicated any information about my cognitive abilities.
The same is true of all the presidents - including the last two. If you don't like Biden then don't like him because of his policies. Laugh at him because of his personality or style or the inevitable hypocrisy that all politicians land themselves in. Not his inability to walk up a set of stairs on a boarding ramp.
The same is true of Trump. Laugh at his bombastic personality and his hyperbole if you like not his inability to stand straight or his tendency to lean like a tree in a heavy wind.
Or do laugh. Laugh at the silliness of a society that elects old men and then expects them to behave like young, healthy people who never experience any of the pains or pangs that it means to be mortal.
In any case, there are no conclusions to be drawn from Trump's wobbles or Biden's falls about their political platforms. For those you've got to look elsewhere. Sorry.