Trump had no coherent message because he's not running on his 2016 platform anymore.
He said nothing about ending wars, the wall and immigration policies and very little about putting American workers first.
Only at the end did he remember to talk about all the judges he installed.
In fact, Biden highlighted his own America First policies and kept saying that Trump had no plan. And Trump never countered him on that unless on healthcare which also went nowhere.
Biden also made mistakes that Trump could've easily slammed but didn't. Every time he picked the most roundabout way at getting back at Biden with something Biden either had nothing to do with or could easily counter.
And Trump just kept talking about anything except what Wallace asked him. When race came up he talked about Law & Order, when the economy came up, he started talking about Hunter Biden.
At some point he started to debate with Chris Wallace: "Sir, we can switch seats if you want"
Trump went from a populist anti-establishment message in 2016 to nervously shouting clickbait lines in 2020.
There was one fleeting moment of 2016 debate Trump, when Biden said he held much smaller events and you could hear Trump say in the background: 'Because no one would show up' and Chris had to hold back his chuckle and even Biden smiled.
And that is Trump's biggest problem. Biden enjoys the Presidential spectacle and is willing to go through the motions to deliver his message and get elected. He doesn't feel entitled to the Presidency.
Hillary Clinton resented the whole democratic process and just wanted to get it over with as soon as possible and Trump actually showed the same sentiment at last nights debate.