How? Because we even know how to spell the word unlike you.
But seriously, go find a little information on the signs of Dementia. Joe is in the mid level of things and given his rants about things from the past that don't really have much bearing to current events you would have to consider a diagnosis by professionals would also investigate Alzheimers.
Example of the kind of info I'm talking about,
What are the early signs of early dementia?
11 Early Signs of Dementia and How to Spot Them
Recent memory loss.
Forgetting how to do everyday tasks.
Problems with language.
Becoming confused in familiar surroundings.
Difficulty in calculating numbers and handling money or balancing the cheque book.
So given the few things in this one example above, I doubt anyone could be taken seriously when attempting to label any of those actions as an everyday situation in Trumps life. Joe's brain is on the way out, Trumps is not. We all in fact exihibit some of those symptoms from our teens but they're not our everyday occurence as seen in Joe Biden and for most people it's only when they're tired etc that they would exhibit anything at all.