because who wants to get into a war of attrition

Someone who wants to actually defeat their opponent for good.

What did American shock-and-awe campaigns actually accomplish? A decade-long counter-insurgency quagmire, and the Americans eventually just picking their bags up and fucking off? Conversely, why did post-WW2 Germany not see any notable insurgency, despite being a state with one of the most radicalized populations in history, complete with dedicated genocide squads and indoctrinated child soldiers? Because they were defeated not in a lightning-fast campaign, but in a brutal years-long war of attrition, which, in the end, left the majority of German men either dead, crippled, or captured - there was no-one left to fight (until a nascent NATO released a whole lot of those prisoners, so they could again be used against the Soviets).

A timeline where the initial Russian offensive works and Ukraine surrenders is a timeline where Russia gets its own Iraq, except it's not halfway across the world - it's on their doorstep. It's a timeline where Azov ghouls, not having been slaughtered in a long war, are driving vans into crowds in the Donbass and setting off car bombs, where schools are being shot up, where there's a dozen Crocus City Hall attacks, where there's a constant trickle of covert Western support (that, unlike the current shipments of tanks and planes and missiles, cannot be found and destroyed on the battlefield).

How often, in history, has an opponent actually been truly defeated, not set back for a couple of years, but thoroughly removed as a strategic threat, by a quick military campaign?

There's this bit from a Big Serge article which stuck with me

Much is always made of Russia’s propensity for “suffering”, with interpretations ranging from a romantic Russian-patriotic notion of sacrifice for the motherland to an anti-Russian criticism of the Russian tolerance for casualties. Perhaps it means both: the individual Russian soldier is more willing to sit in a freezing trench and trade shells than his adversary, and the Russian state and people are able to lose more and last longer in the aggregate.

I rather think, however, that Jünger’s metaphysical “titan of suffering” is not so metaphysical at all. It rather refers to a mundane power of the Russian state, namely its excellence and willingness across the centuries to mobilize huge numbers of men and material for war, at the expense of other social goals. War with Russia sucks. It means mass casualties, cold trenches, scarred earth, and long nights of shelling. The Ukrainians have coped with this as well as anyone (because they are themselves quasi-Russian, however much they deny it), but it is an awful thing to trade shells for years on end. The Russian power of suffering is to willingly fight wars that devolve into bat fights, knowing they have a bigger bat.

also who remembers the T-14 Armata? that was fun

Russia ditching a wunderwaffe and re-focusing on producing well-proven and reliable equipment is, if anything, a testament to them being smart, and adapting well to the conditions of the war. It's the "Germany should have just ditched the Tigers and made more Panzer IVs" hypothetical playing out in real time (although admittedly, Nazi Germany's case is a bit more nuanced, since even if they had made larger numbers of cheaper tanks, they wouldn't have actually had the manpower of fuel to use them - so making a smaller of amount of more capable vehicles was perhaps the right choice for them, or at least it would have been if said vehicles actually were capable and didn't tend to break down before even getting to the battlefield).

Conversely, Western militaries are just sticking their fingers in their ears about this whole war - they mocked "cope" cages for a couple years, until they started installing them themselves. They're still doing the "drones aren't a problem, we'll just knock them out of the sky with jamming/lasers/magic" cope, years on. They just whipped out a microwave cannon (which, well, hope you're one of the maybe 10 units that gets one of these, sucks to be all the other guys who have nothing and still get blown up since something like this would be exorbitantly expensive to field and deploy), and the batshit new Army manual about, uh... waving your hands frantically and shooting drones with tanks?! They're far behind on integration of drone teams, despite the fact that the Ukrainians are literally sitting right there doing it.