Russia should have waited 20 years to attack Ukraine. The West will have dismantled their military by then. So all they will have to do is to walk over and seize the territory by then. Ukrainians will more likely to be indoctrinated by the West so they'll be less likely to fight for their country.
Well, maybe. Russia would have had to overcome its primal instincts and figure out how to quit driving overall public opinion in Ukraine toward growing nationalism and away from disgust and distrust of Russia due to Russia’s activities in Ukraine.
Relatively unhampered and seemingly not threatened by Russia, in 20 years Ukraine would have also likely become a major competitor to Russia’s energy exports, exactly what Russia feared.
Where US politics might swing in 20 years could be very uncertain.
Since I don’t think Russia actually could overcome those instincts (and the behaviors that follow), and since at least some Euro NATO countries actually have been pushing toward their NATO defense commitments the last few years, and NATO has in fact been busy training the Ukies, while I’d not expect serious strengthening of NATO, depending on it to “dismantle” seems a bit optimistic for Russia’s purposes).
And... of course it’s highly unlikely Pooty would still be around in 20 years: While I think he’s only a symptom of Russia’s overall system and direction, the “when” of a move IS considerably dependent on him while he’s in power, and IMO he wants mention of significance in history as a Russian “hero”. “The restorer of the Motherland” and all that...
My own projection of an optimum course for Russia would be to interfere in the 2026 elections to ensure Bidet gets re-elected. Adopt a temporarily conciliatory position regarding Ukraine, but negotiate-delay-negotiate-delay any real retrenchment, get the claws fully into Europe’s energy supply and undercut competition. Strike in early 2029 or early 2030.
But, that’s just my guess.