I was thinking the debate rules actually saved Trump from his worst impulses. Biden was allowed to speak at full length and Trump gets to appear like he can participate in a civilized conversation while Biden would sometimes go off the rails while trying to fill his time. A lot of his embarrassments started in a decent place, but pivoted badly in the middle.
Trump confidently lied repeatedly without consequences, and so long as someone is unaware that it’s lies, I could imagine them finding Trump’s rhetoric credible that night.