What a complete rationalization. Friendly and hostile governments come and go in all countries. Ukraine is not a vassal state of Russia in which Russia has the right to a friendly government. Nor was Russia’s naval base at Sevastopol threatened by the new government. Rather, Putin coveted Crimea and used the events in 2014 as an excuse to grab it. Overall, as he has indicated in multiple addresses, Putin does not accept Ukrainian independence and wishes to correct Lenin’s big mistake and reabsorb it back into Russia, regardless of the Ukrainians’ desire for independence. Everything else is just an excuse for this ambition.
Of course it's a rationalization; sometimes we ourselves oust hostile governments in favor of (hopefully, but not always successfully) more friendly ones, depending on the circumstances. It does not render the underlying geopolitical reality any less true.
Ukraine is not a vassal state of Russia in which Russia has the right to a friendly government.
Countries which lie between more powerful nations can either play the game of neutrality wisely, or decide to poke at one Great Power in the hopes that another Great Power(s) will come to their aid (even if it's not in the interests of the other Great Power(s)). This is the historical reality, whether we like it or not.
Nor was Russia’s naval base at Sevastopol threatened by the new government. Rather, Putin coveted Crimea and used the events in 2014 as an excuse to grab it.
Strange, then, that Putin decided in 2010 to extend the lease of Crimea's naval facilities from 2017 to 2042; said lease had been in existence since 1997. One might think that the Maidan Revolution (and the West's involvement in same) in 2014 changed Russia's political calculus with regards to Crimea (especially given that the infamous 'little green men' didn't show up in Crimea until days after Yanukovych was ousted), but you might consider that too obvious an observation.
Overall, as he has indicated in multiple addresses, Putin does not accept Ukrainian independence and wishes to correct Lenin’s big mistake and reabsorb it back into Russia, regardless of the Ukrainians’ desire for independence. Everything else is just an excuse for this ambition.
Until the pro-Russian government was ousted during the Maidan Revolution in 2014, Putin seemed content at letting Ukraine be an independent nation. However, when a historically antagonistic military alliance (that being NATO) continues to send signals via overtures to Ukraine's government that its continued eastward extension to Russia's borders (which has long been declared a red line across the Russian political spectrum since the '90s) is of high probability, that only increases the likelihood of Russia using political, economic, and military force to secure its interests in Ukraine (much like America has with the Monroe Doctrine).
But I digress: this whole mess is just another continuation of a longstanding ethnic feud amongst the Slavs. I maintain that America had no reasonable geopolitical interest motivating involvement with one side or the other; if bleeding out Russia was truly so important to our national security, then Congress should have drafted a declaration of war against Russia. (But we know why that would never happen.)
Instead, we seem content at depopulating our military's equipment stores so that Ukraine can fight to the last Ukrainian.