If he told the Ukrainians he would no longer support them diplomatically, financially and militarily and he would do everything possible to discourage other nations from doing so then he might coerce them to accept a "deal" from Putin.

Trump could coordinate a diplomatic maneuver with the Kremlin so the latter would promise to freeze its advance on the ground and refrain from further bombardment IF the Ukrainians made certain concessions, like agreeing not to join NATO and disarming, perhaps even the resignation and exile of Zelensky. It would allow Putin to withdraw and save face (providing the details were kept secret from the rest of the world until Ukraine signed on). Facing certain defeat and occupation by Russia and further destruction of their country, Kyiv would have little choice but to accept these conditions.

In spite of their bravery and resolve, the Ukrainians simply cannot defeat Russia and its allies without massive military and intelligence support from the West. And I believe this is precisely what Trump is planning to do once he is President. In fact, I wouldn't be a bit surprised if Trump isn't already in contact with Moscow over the details of this transaction. Trump will never forgive Ukraine for refusing and exposing his attempt at blackmail over the "dig up dirt on the Bidens" scam. The future of Ukraine, the EU, NATO and eventually, Taiwan, is irrelevant when Trump's revenge is concerned.

Of course, the long term success of this deal would depend solely on Russia keeping its word.