My take:
Russia has been attacked many times in their history. Some are their own fault, others not so. It's in their psyche to be alarmed at the thought of an invading army. Napoleon did it and then Hitler gave them catastrophes to which the world has never seen before or since.
Since the Soviet Union broke up their main fear has been their Western flank going to NATO or EU. Ukraine by its nature is very flat in large parts and very easy for an invading to gallop across right onto Moscow. Napoleon and Hitler did that to devastating effect and almost ended the Russians as a nation. Ukraine going to NATO and EU would have been a disaster for them, just like Mexico, Canada going to the Warsaw Pact would be for the US. I have travelled extensively, even lived in Eastern Europe, I still hold permanent residence there, there is no way those countries based on their economies or their corruption level be ready for EU or NATO. The only reason they have been put in NATO and EU is to isolate the Russians. Absolutely 100% anyone who's lived there would say the same.
Ukraine have been daft in how they went about this, they could have been neutral and said we realise ancient relations with Russia and we want to be part of the European family too and maybe we can bridge tensions between EU and Russia by staying neutral. And gradually down the line they should have consolidated their strength enough to deter Russia. Just like Russians have not gone near Finland. I am not saying this might have worked either but their current way didn't work either. Afghanistan should have done the same, when these countries are so poor and corrupt with little military power then showing a spine with nothing to back it up against is very bad tactics. I am not sure why Pakistanis are confused understanding this, as we have the exact same fear with Afghanistan hence us supporting the Taliban through the years.
Again please don't attack me, what Russia is doing is wrong BUT from THEIR POV this is their thinking.
Now when it comes to the war going on right now:
Ukrainians said 4000 Russians died. Russians said only 2 died and then next day 500 died, so the truth is probably a 1000 dead. In a week. It's horribly poor.
Their ruble is now 121 to the dollar from 78. A week more it'll be Rupee level, sanctioned by every western company from Apple to Microsoft, their national airline about to go bankrupt, their biggest tech companies defaulting, they haven't opened their stock exchange yet either for a week, they had saved 650 billion dollars for this war, most of which they can't probably access now, all Putin's rich oligarchs sanctioned, for a country who spends 70 billion a year on military this is back breaking Their 50 miles long convoy outside Kiev still stuck, bogged down by breakdowns, stuck in mud. Twitter has audio of their soldiers talking from different units, no secure lines at all, their tanks on so many motorways stuck without petrol and being goaded by Ukrainians who ask them if they'd like a lift back to Moscow. They dropped paratroopers the first day near Kyiv without any back up or logistics, who were then routed. It's like they just went in without logistics or any planning, no supply lines, no support, nothing. Scores of videos online show Ukrainians climbing Russian tanks or lying on roads and the soldiers back away. They will win eventually but it's been a sheet show for them from start to finish. And even if they win and install a puppet, there is no way that puppet won't be overthrown.
Any country on their borders will have no fear of being rolled over.
NATO share massive blame too, they know they can't face Russia directly so are throwing the Ukrainians under the bus, goading them more and more. And the result is destruction and civilians getting killed.