It’s not Trump. The one right before he tested positive for Covid was a disaster. He took Biden’s bait, he took Chris Wallace’s too.
Reagan’s first debate with Mondale was a disaster, to the point, where even Reagan’s people thought he might blow his re-election. Then came the second debate when Reagan said, “I want you to know also I will not make age an issue of this campaign. I am not going to exploit for political purposes my opponent’s youth and inexperience.”, and the rout was on!