I will still say Russia/Putin didn't have much choice but to try to stop expansion of NATO and that "recognizing" 2-3 "new" ethnic Russian countries seemed a slick first move. A little incursion into Ukraine, I also think, much of the world would have eventually forgiven.
It looks like Buchanan expected something similar to what I expected: scare Ukraine into forswearing NATO & weaponry and then retreat, with very few civilian casualties:
https://buchanan.org/blog/is-putin-considering-using-nukes-on-nato-159130
Somewhere during the adventure, I expected China to take Taiwan (it isn't credible that Russia and China didn't collaborate on timing, etc.). I wasn't sure how China would do that, but I expected a surprise, using some means that wouldn't destroy too much infrastructure.
That would leave NATO, EU, and - especially US - with a huge loss of prestige. I view the US/NATO military as nowhere hard-combat ready (and posted those recent recruitment videos from the three countries to demonstrate just how laughable/ demoralized the US military must be to be running ads recruiting LBGTQ+ and with President Sundowner in charge.
At this point, however, Putin has gone further than I expected, and I want to acknowledge that.
If something doesn't break to the positive for him soon, I don't see how he can withdraw. I also don't see how he can take and keep WESTERN (as opposed to eastern) Ukraine.
If China is going to move, I would expect that very soon...
If SOMETHING doesn't happen soon to relieve Russia's pressure, I think Putin has a growing problem with economics and popular support, both within and without Russia.
It should be interesting. I guess I am saying, in a round about way, that your "World War" call is beginning to look less implausible to me. I still don't think it started with this invasion, though, and I still don't think we (the plebs) know the half, nor even the one-quarter, of the full, real story.