This was actually in breach of at least two treaties between eu/NATO and the Russian Federation. This is the root of why Russia has now resorted to "techniical means" to solve its perceived security issues. They tried for the last 8 years to get people to listen to them, but no one was interested.
This is actually not what happened. Russia not only didn't invade, but Russia refused to acknowledge the referendums asking to allow the two "breakaway republics" to join the Russian Federation. Why didn't Russia just bite off the east of the Ukraine then and there, when it was offered? The two areas declared independence because they didn't want to be ethnically cleansed - people were locked in buildings and then burnt to death, civilians were strafed by fighter jets at a market - little things that get forgotten. Russia didn't invade (although there were claims of "little green men", an invasion is what you are seeing now, not 8 years ago).
The west did a lot - they spend $5 billion on building up an armed insurrection that toppled the government. The USA in the guise of Victoria Newland is on record overturning the head of state, selecting which billionaire gangster would be the new king etc. Interestingly Victoria Newland is married to a Mr Kagan who's sister runs the think tank that the BBC and everyone else use as a source of expert knoledge:
Institute for the Study of War Just to be clear, the West created the situation we are now in, purely for the purpose of "putting pressure" on Russia. 14,000 dead people later, Russia finally intervened only when it was clear that the Ukrainian government (pressured by the USA) were about to invade the Donbas, again purely to put pressure on Russia. In other words, we broke it, so we now get to own it.
The current conflict is entirely due to work done by the west. The Russians tried to resolve the issues, tried to get agreements, sponsored the two Minsk agreements. No one in the west had any intention of honouring these solutions because the plan was always for war.
Russia has confirmed repeatedly that they view this as an existential war. Biden has said that "Putin must go", and that Russia must be broken up (ie cease to exist). Russia (Putin himself) has explained that a world without Russia serves no purpose, so has no reason to exist. That was a hint. Are you
sure you want that?
As mentioned in various places - fight to the last Ukrainian. This is now happening. Various estimates have Ukranian casualties at over 100,000 (more than the entire British army, for comparison). Most units seem to be 60%or more under strength, with the majority of soldiers on the line untrained new conscripts, who are dieing in droves. The Ukraine will be calling up women from October, and has just passed a law allowing conscription of disabled persons. Winning! What could possibly go wrong?
Here is an alternative view of how we got to where we are, and how:
Jacques Baud: The Military Situation In The Ukraine - Update. - Labour Heartlands