If they knew about it in late 2020, that info must not have made it to the upper levels of the military, given how much crying and foot-dragging they engaged in when Trump tried for his (IIRC) 90-day withdrawal. One wonders how ready our military actually is if they act like moving low-thousands troops of and some equipment out of—not into!—a theater in which we control the airspace, within in a couple months, is a crazy thing to ask of them. It may have been a bad idea to withdraw that fast, sure, but some of their spokespeople they had on the circuits whining about how hard it was weren't saying it was a bad idea, but that it literally couldn't be done. Sure, Jan. Certainly, if The Shadowy Figures That Control Everything (riffing on the vibe of GP's post) had already decided we needed to shift to Ukraine, that was still a closely-kept secret in late 2020.
And I'm not as sure as GP that Biden's following through on the withdrawal was because of Ukraine, but I'd also not rule it out as extremely-unlikely—the timeline is such that it's possible.
Another fun exercise is to ponder how much - if any - influence Trump's supposed ties with Russia have on these hypotheticals. There was some other issue, recently, whose details have since slipped my mind, that made me think, "Oh, this 100% makes sense if you assume that Trump is being told to do Thing by a party who is trying to weaken America's position ahead of a resumption/escalation of 2014's hostilities." I believe it was something that Democrats uncharacteristically reversed course on, which, again, would lend credence to the notion that this was something of a clandestine pitched battle from the start. I wouldn't rule it out. Not from a Secret Society Ruling The World standpoint, more like Leaders In A Desperate Position Pulling Out All The Stops.