In 2010 President Yanukovych was elected President of Ukraine. International observers did not claim the election was unfair. As an Eastern Ukrainian with sympathies for Russia in 2014 the President rejected the draft EU Association Agreement and opted for closer ties with Russia. This was highly contentious in western Ukraine and led to protests. Some think the EU and the US encouraged the protesters, leading to the resignation of a President who could no longer keep control. His replacement led Ukraine to an EU tie up. Russia sent in troops to Crimea, took control with no resistance and held a referendum. They claimed 97% support for their takeover on an 83% turnout. There were no western observers or audit of this result, and the two choices did not include the old status quo. Subsequent independent opinion polls have shown a high level of support for the results of the referendum anyway, just as independent polls before the annexation showed majority support for closer links with Russia.
Western policy has failed towards Ukraine. The UN did on a majority vote condemn the Russian actions and called for the restoration of Crimea to Ukraine, The Western powers rightly did not seek to claim Crimea back by military intervention. To this day they have said Crimea should be returned but have ruled out military involvement. It would kill too many people, and it would be difficult to impose Kiev and EU rule on many people of Russian origin in Crimea who prefer Russian rule.
All this is topical again because some other parts of Eastern Ukraine are in revolt against Kiev rule and have sympathies for Russia. Russian troops have been massed on the frontiers. The West led by President Biden has told Russia not to invade and has threatened penal sanctions were they to do so. What is clearly needed is a political solution in Eastern Ukraine that works for its people. The eastern voters have little chance of winning an countrywide election in Ukraine any more, unlike 2010, because their numbers have ben reduced by the loss of Crimea.
Ukraine is the political battleground between EU and Russian influences in Eastern Europe. The EU and US misjudged the situation badly in Crimea when they pressed the EU Association Agreement against the wishes of the then President and lost a part of the country. They need to be careful not to misjudge again.