[adventured]

The response from Putin is because the window to conquer Ukraine and force it back under the control of the Russian Empire that Putin dreams of, was closing. He knew that if Ukraine got too built-up militarily, or got too close to NATO, his opportunity would vanish. He similarly dreams of reclaiming Belarus formally. Putin hasn't been shy about any of this, he openly admits the lust for conquering former USSR territory and rebuilding the empire.

Putin lied and claimed a big part of the core issue is not wanting NATO's borders moving any closer. So he attempts to annex Ukraine into the empire and move borders closer to NATO. Obvious lies are obvious.