Just my two pennies.. Personally, I wish we could discuss the issues surrounding this case without rancor and accusations.
As I see it, the situation is clear. Perhaps you don't agree, but if you use rational explanations and evidence, perhaps more will understand.
Here is how I see it;
1) As the USSR sputtered out in the early 1990s, the numerous client states saw their chance to escape the gulag ridden empire. Thus, most of them chose freedom and independence. The map of the USSR changed post haste, by shrinking greatly back to the old Russian borders.
https://www.jstor.org/stable/3992775 2) Each of the east European states progressed very well, elevating their economies and enjoying
their new found freedom.
3) As in Russia and some client states, there are some who for whatever reasons, are longing nostalgic for the "good old days", when their lives were ordered for them, by the central planning committee.
4) One who longed for this, was a man being trained and indoctrinated by the KGB. Vladimir Putin
was driven by the idea of reconstructing the USSR. Missing the old "glory days", he set about to execute his plan.
5) Evidence of Putin's compulsion? Kazakhstan, Crimea, Donets and warnings against the Baltic nations against joining NATO.. He has already made Belorussia a fresh client state.
6) Obama encouraged Putin by caving to his demnds, by removing defensive missiles from NSTO member, Poland.. and rewarding Iran's ayatollahs for their abhorrent behavior.
7) When we elected Pres Trump...that put a crimp in Putin's reconstrution plans, an dhe was very quiescent during Trump's tenure. Then came the robbed election that placed a demented old man in the oval office.
Obviously, Putin watched closely, in order to assess his chances...and when he saw that Biden was once more trying to reward Iran, he was encouraged. ..But the desertion of so many people and so much military equipment in Afghanistan..clinched his decision..
Still, any real conflict if troops are needed, Europe is the one who should reach out to the Ukraine.
OK..now hurl your brick bats !