The world is full of trolls and some people have mastered trolling. Whoever did this to Biden, when you type in www.Biden.com, has mastered trolling.
When you type www.Biden.com, you expect to be taken to some kind of pro-Biden website that may be telling you how great his policies are or, raising money for his campaign, etc. Instead, the URL redirects you to a website taking donations for Alzheimer's research.
It has been an on going theory that Joe Biden is breaking down mentally because he is getting older. This is almost apparent to anyone that has listened to him speak for longer than 30 seconds. He slurs his words, stutters, and down right forgets what he is talking about mid sentence. So it is not a surprise that someone made this URL redirect to a Alzheimer's research domain.