Eastern portion of Ukraine is heavily in favor of joining Russia as most speak Russian while he central and western parts want to join the EU but this is largely a one sided love affair. EU has repeatedly stalled and delayed Ukraine's membership seeing that it would be the second poorest member state after Greece, and thus would be against the interest of Germany, who stand to gain a lot by using Russia's gas pipeline.
Enter Maidan revolution, while not outright instigated by the US, one does raise questions about the role of Facebook in previous revolutions namely the Arab Spring movement, Syrian rebellion, etc, and how quickly they were able to spread a the Maidan propaganda that EU/NATO membership was imminent when it couldn't be further from the truth.
The 2014 invasion was relatively well restrained campaign at reminding who the master of Ukraine is which was promptly ignored by the following administrations. Rather than choose peace with Russia by remaining neutral, they chose to go down the impossibly difficult act of trying to gain NATO membership with a border dispute in Donetsk/Lukansk region.
It might very well be said that Putin planned to take Ukraine anyways and 2014 was a test run and a good platform to encircle and hook into Moldova, another potential hotspot. The fact remains that leaving the Ukraine flatlands to NATO troops would open up Moscow to an indefensible flank, the upkeep cost of maintaining a wide frontline the size of Ukraine-Russia border would bankrupt Russia.
Simply put the cost of inaction was calculated to be far greater than the risk of action.
Imagine if you will, Mexico wanted to join China's security umbrella and it was receiving Chinese troops, tanks, hardware right across the US-Mexico border. Next Canada joins the party.
How quickly do you think the US would put down such strategic positioning?