Everyone knows now that he's in way over his head. He's lost. He can't fake it anymore. He has a record now of total and complete failure that he can't hide.

And as the writer said:

"“The incumbent is always in this little trap of ‘what can you promise?’” said Martin Sweet, an assistant visiting professor of political science at Northwestern University. “Anything he talks about, he is going to get slammed on: ‘Why didn’t you do this before?’”

Yes, why didn't he do it before? Because he's incompetent, that's why. And at least people know that for sure this time and can vote accordingly.