Shivering That's it in a nutshell.
Right now he's doing everything and anything he can to appeal to his base and to 'undecided' voters whom he believes to be as racist and greedy as he is. He doesn't know how to appeal to voters without rhetoric and ugliness. He's like a carnival barker screaming "Step right up folks, and see the 8th Wonder of the World....ME!!!". Gilderoy Lockhart in real life.
His public persona has always been bombastic and mendacious, in every business deal he's made you can see him touting the 'magnificence' of whatever property he's shilling for. And it's always lies and 'alternative facts'. And then he quietly walks away or 'breaks' whatever business is at stake, knowing that his team of lawyers will get him off the hook as cheaply as possible.
If he truly accepts that he's not going to be reelected you are right, we are going to see a shitshow the likes of which we've never seen. But I don't think he actually believes he isn't going to be reelected. Either because his ego won't allow him to believe it or because he's planning on rigging the election.