You might have thought that if you were selling the narrative of a gaffe-prone, senile, sleepy, basement dwelling, drugged up opponent that if there were kernels of truth in that line of attack you would give Biden enough time and space to hang himself.
Seems like Trump did the opposite and by constantly interrupting and over-talking denied any opportunity for Biden to descend into a rambling stream of consciousness.
Perhaps after 4 years of people fawning over him Trump can no longer cope with direct criticism of his "achievements" and personality so lobbing firecrackers every couple of minutes was preferable to listening to someone talking him down. Even if the latter approach was more electorally beneficial.