Why? He can't run for a third term (legally). If he did, enough states would disallow him on their ballots that he would have no chance of winning. So, he's gotten the most he can wring from this stint. Why would he care afterwards?

Because his worst nightmare is to be directly succeeded by a Democrat.

First, with all the stuff that this Administration has been doing (and will have been doing) that skirts the law, Trump does not want a new DOJ starting off in January 2029 doing investigations into everything. He might have some personal immunity from criminal liability - but all that money? All his partners? All his companies, and family members, and everyone? Trump doesn't want that stuff being looked into by prosecutors (for everyone but him) or the civil division. They're going to have a field day going after all his amazing "deals."

Second, almost everything he's done has been done through Presidential fiat - executive orders and just telling folks on Truth Social what he wants. Which means virtually everything he's done can be undone just as informally. The monuments can be torn down, the renamings undone, the Trump currency cancelled...everything. If stuff sticks around for another four years under a Republican successor, the urgency of that effort passes and some amount of inertia sets in.

And third, he wants to remain powerful in the party. Having your chosen successor lose will weaken you; having them win gives you continued strength and influence.

At some point in the late spring, you'll see Vance and Rubio and/or some unknown Trump selection all doing their various campaign launches. Trump absolutely does not want those campaign launches to be set against the backdrop of $4.25 gas prices and discussions of the anniversary of the ongoing Iran quagmire. Because it's bad for him.