Ukraine has a severe manpower problem, while Russia hasn't even implemented full mobilization yet. They can keep grinding down the existing defenses until there are simply not enough Ukrainians in uniform left to hold the tide, and then things would break down pretty quickly in the absence of external support.

They would still have to contend with an insurgency on occupied territory, but that is something Russia has considerable experience with, including Ukraine in the past (mopping up the remaining nationalist resistance after WW2).

Slowly then suddenly. Movements in the frontline are gradual until one side is exhausted and collapses. With Trump’s ludicrous “peace” plan, Ukraine would be barred access to US weapons, the size of its military restricted, and Russia would simply rearm and try again.

And despite how things have fared in Ukraine thus far, the Baltics are a much softer target. If Ukraine does end up falling to the Russians, it’ll be used as a springboard by the Russians, potentially supported by Ukrainians disillusioned with the West’s betrayal. It would certainly not be the first time that Russia has annexed Ukraine and mobilized its people against Russia’s foes.