The problem is that the Trump and Biden camps set the rules at this debate.
The moderators were not allowed to live fact check, nor could they cut the candidate’s mic during their allotted time.
This means that the responsibility of countering Trump’s lies fell completely on Biden. There are so many lies, it would be a difficult task for any person.
But Biden signed up for this, and he failed spectacularly. None of Trump’s bullshit was effectively countered.