It's not desperation, its not his money and if it actually happened, it would hamstring the incoming Dem president in 2028:
“Only I can make this promise to you,” he said, adding that the Republicans would have to win both the House of Representatives and the Senate for the money to be paid out.
And not only wouldn't it be his money, it wouldn't even be "real" money. There's not a trillion dollars laying around for this (literally what it would cost).
Since Trump's first term in 2016, the debt has doubled from 19 trillion to 40 trillion. This will get tacked on and the debt will be used as an excuse not to fund social programs.