This is one of the incoherent arguments of the pro putinists.
1. They assert that Nato is/was weak and unprepared for war;
2. They say that Putin was so threatened by Nato that he was forced to invade Ukraine.
1 & 2 are incompatible positions.
“Here was a manifestation of a huge, historic British folly, repeated over many centuries including the twenty-first: the adoption of gesture strategy, committing small forces as an earnest of good intentions, heedless of their gross inadequacy for the military purpose at hand.”
― Max Hastings, Catastrophe 1914: Europe Goes to War
I will go with option number 1 as a primary factor.
As a side note, I expect that Putin truly believed he could take down the Ukraine in a week, and there would be no effective countermoves from NATO. See that option #1 again.
It is always dangerous to believe your own propaganda.
Every war starts out with an accumulation of incompetent commanders. They make lots of horrendous mistakes. Winning armies purge those guys pretty quickly. The Russians are well advanced into this unpleasant education. And NATO? That remains to be seen.
As for option #2? I have no doubt that Russian paranoia was a factor. The Russians have a long history of being invaded from the east and the west. It is ingrained in their culture to see threats everywhere, even from supposedly weaker and inferior forces. They are not wrong either.
I see no impossible contradictions in #1 and #2. People often act from conflicting and incompatible beliefs. In any case, option #2 makes a great rationalization when you need to rally public support from the Russian people. Whether we believe it or not does not matter. They do.
At the core, the Ukraine project was a land and resource grab that looked like it was going to be easy. Refer back to that option #1. All the gas and oil deposits are in the eastern part of the Ukraine, along with the greater concentration of Russian nationals and descendants. Knocking out western Ukraine and demilitarizing the area was going to be a bonus.
Why certainly, the mighty Russian army could take on this project with a six-axis combined force attack and get it all wrapped up in a month. Except that they couldn't.
What actually happened should be an object lesson in the consequences of believing your own propaganda. Let us not make the same mistakes.