Once upon a time Great Britian and Russia competed for control over Central Asia. It was called the Great Game. The British had acquired India and had influence in other areas in Asia and were concerned about Russian expansion close to India.
It was reasonable for the British to be concerned about an invasion of India from the northwest as every other conquest of India besides the British conquest had come in that direction. The British went into Afghanistan and resisted Russian expansion.
The British had also contended with Russia in the Black Sea region and the Balkans, as well as competing interests in the Far East.
In some ways America inherited a pre- existing power struggle as the US took over the British position in geopolitics. Pax Britannica became Pax Americana. And though America established an informal empire based upon trade and alliances, it still took over the ocean power based empire from the UK.
It is almost a given that Eurasian continental powers are the default enemy of the ocean empire. It is easy to divide the world up in a bipolar fashion, after all.
One of the key factors of the ocean empire is to not let the vast landmass of Europe and Asia to be united in opposition. Britian has had the policy since at least the 1500s to unite smaller states to oppose the greatest power in Europe, whether it was Spain, France, or Germany. It also opposed commercial rivals like the Dutch.
And America inherited this position. It didn't matter about the actions of countries. Instead it worked to weaken its perceived rivals.
When the Soviet Union fell, there was no reason to continue to contend with Russia. America had its unipolar moment and gradually created its Rules Based International Order.
By that point, almost every American foreign policy expert was locked into the bipolar paradigm. America had never really participated in multipolar diplomacy in the 19th century and just didn't have the basis to do so. America's political system is a bipolar system instead of the multiparty systems common in most Western nations. Third parties largely are meaningless spoilers domestically so many American politicians just don't understand what do when you can't just dictate one way and call opponents “the enemy”.
Because of this mindset America has worked for 30 years to create in Ukraine a proxy state to harass and contain Russia. They don't care about Ukraine or its people. It was very telling that it came out during the impeachment that Col. Vindman, of Ukrainian heritage, didn't speak Ukrainian, and that he had been considered for a high office position in Ukraine.
Anyway, the USA dumped billions into Ukraine, conducted 2 color revolutions in Ukraine, and gradually built up the Ukrainian army for a combat with Russia. Careful observers could see that there was a planned conflict in 2017 that was delayed by Trump's election.
So why did the US and NATO build up Ukraine for war? It is a continuation of long efforts to weaken the landmass power. Russia was looted and devastated in the 90s, but the West didn't envision a recovery. Putin in his early years ruling Russia sought for inclusion with the Western alliance and cooperated. It was Putin’s ability to bring Russia back that put the target back on Russia.
During the end of the Bush 43 era, the Western leadership picked its new target after the Middle-eastern conflicts played out. The need to limit and contain Russia became imperative, even though the US has acted as the expansionist aggressor power for 30 years.
The war itself, in spite of intense propaganda to the contrary, appears that it will lead to a partition of Ukraine. It is only a question of how many will die before real negotiations take place.
Breaking out of a paradigm is near impossible for most. Moving to a multipolar world will bring about increased peace to the world. Getting there will be brutal.