I think I figured out why some people think Trump won, as opposed to Biden losing. It's the WWE effect. The whole self promoting, loud mouth, obnoxious braggart act is right out of professional wrestling.
In the minds of Trump and his minions, a debate is a verbal brawl, an exchange of insults, candidates shouting and shaking fingers at one another. What Trump tries to do is smackdown his opponents.
During the 2016 Republican primaries, his crude, mannerless behavior completely flummoxed his Republican opponents. He even left Jeb squirming and stammering. I don't think they were prepared for such uncouth conduct.
Biden soundly defeated him twice just by remaining cheerful, sticking to policy, and talking directly to the audience.
It would be interesting to see what someone with a good command of facts could do, skillfully calling out his lies. How would Trump react?