Trump's object is probably a reset with Russia which he might hope will lead to a detachment of Russia from China. So far, these might be's have cost us NATO, Canada, Denmark and the trust of Pacific rim nations.
The stakes are high, one can only hope that Trump can pull this off.

Well, since POTUS is the one holding ALL of the cards, it stands to reason that among all of the negotiations Rubio is tasked with a security guarantee - a 2-WAY STREET, btw - for Europe which would torpedo the hawks there and temper the tensions which they are now fanning.
I am not an insider, but my read of the media is nothing more than hysterical reactions, not an international crisis spawned by DJT actions.
Newsflash: Ukraine has been an obstacle for at least two decades.