May be his reasoning went something like this:
Finland and Sweden may not be formally part of NATO but if push comes to shove they’ll probably join any NATO effort, may be even formally join (as we see it happening now)
Ukraine is about to go that way too, I can’t do anything about Finland and Sweden but I can force Ukraine out of the NATO-joining path, be it by ultimatum or outright force.
I think the very menace of Russian forces in the border ready to act if Ukraine tried to join NATO, plus NATO’s reluctance to allow members with ongoing territorial disputes (Like Donets and Crimea) would’ve been enough to keep Ukraine out of NATO without any (more) extreme measures on Russia’s part.
But may be Putin had different intelligence about that…
I think the only thing in Putin’s mind was the megalomaniac idea of recreating the old USSR with him as the Supreme Leader. And beyond that, taking all of Europe.
Everybody’s got a plan until they get hit in the mouth
or more formally
No plan survives contact with the enemy intact
If your plan does not take into account the other side’s reaction you don’t really have a plan after all.
Final step completed for Sweden:
And Finland was already admitted:
So both Finland and Sweden are now full members.
Putin needs to get acquainted with this word:
crapification
(n.) when the ramifications of a certain decision will yield disastrous results of epic proportions.
I am waiting to see what the effect on Putin’s blood pressure would be when or if Ukraine and a westernized Belarus join NATO. (Don’t expect either to happen, but…)
Putin did, of course, invade the Crimea in 2015 with few significant consequences or lasting global outcry. Countries were not rushing to join NATO at this point. It is probably fortunate that the global reaction this time around was very different.
Here is a gift link explaining what the new changes mean in some geographic detail. (More Baltic Sea, Arctic and Northern Border exposure).
Hitler apparently thought something similar after taking the Rhineland, Sudetenland and Czechoslovakia with nothing worse than grumbling from the west.