Frankly, I place most of the blame for that on the US and the West. During the Cold War, NATO's reason for being was to protect western Europe from the Warsaw Pact. Then in 1990, the Warsaw Pact disbanded. But NATO was determined to continue on, despite having became an alliance without a purpose. There was lots of talk about defending Europe from external threats, but the only halfway plausible conventional military threat was Russia. So if only out of habit, NATO remained an anti-Russian alliance.
You are right, but the former Warsaw Pact nations were not in the habit of being members of NATO. Yet they all rushed to join NATO, as did the former Soviet Socialist Republics of Lithuania, Latvia, and Estonia. Did they also believe that Russia posed a military threat to them? And why have Finland and Sweden, formerly non-NATO countries, just recently joined NATO? What convinced them that Russia posed a military threat to their security? Any ideas?
And that in turn played into the hands of the old style cold warriors in the Kremlin. NATO expanded into the former Warsaw Pact countries of eastern Europe. It even swallowed the former Soviet Baltic republics. Those moves were naturally seen as hostile in Moscow. But for 25 years, Russia tolerated it.
NATO did not expand into those countries. Those countries expanded into NATO and the EU by their own choice. Russia itself signed an agreement to respect Ukrainian sovereignty in exchange for Ukraine giving up its nuclear arsenal--an agreement that Russia violated by invading Ukraine in 2014. Which did nothing to lessen the perception in former Warsaw Pact nations that it had been a good idea to join NATO.
Then in 2014, Russia's enemies started moving into Ukraine. Due to deep historical and ethnic ties, this was totally intolerable to Russia. Western deep state agents helped engineer a coup in Kyiv that overthrew a popularly elected pro-Russian president. Anti-Russian elements were place in power by mob action in the streets. So Russian hard liners replied by a bloodless annexation of Crimea.
What enemies "started moving into Ukraine"? Who did you have in mind? No Western "agents" were involved in the Maidan revolt, but US diplomats tried to mediate between protesters and the Yanukovych government before the government started to use violence to clear the protesters. Yanukovych was never very popular, having lost his first bid for election after election rigging was discovered. That triggered a nationwide protest against Yanukovych's victory called the
Orange Revolution in 2004. He was easily defeated in a runoff, but Yanukovych narrowly won his second bid in 2010. When he began trying to move Ukraine away from Western Europe and integrate more closely with Russia, the Maidan protesters assembled in Kyiv again. This was all documented thoroughly in the press. You can find an excellent documentary record of it on Youtube:
Winter on Fire.
Then for years, the Russians were quite explicit that any NATO expansion into Ukraine would mean war. It was never a secret. But the US and Europe believed that it was just bluster and refused to back off, and in 2022 the Ukraine War started and continues today as kind of a World War I style stalemated war of attrition, as hundreds of thousands of young men are killed and maimed and the world lurches ever closer to nuclear war.
Russian threats were taken seriously, and that is why Ukraine was never admitted into NATO. It still isn't in NATO, but, thanks to this illegal, unprovoked invasion, it almost certainly will be admitted. The event that triggered the Russian invasion was the Maidan revolution, which posed no threat at all to Russia. Russia invaded in the aftermath of Yanukovych's ouster, although they pretended that they weren't sending troops into Ukraine until it became obvious to everyone that they were doing just that.
Yet even today, many politicians in both the US and Europe still demand that Ukraine fight until Russia is "defeated". But what would a Russian defeat look like? Regime change in Moscow? That would most likely result in even more hardline nationalists taking power. Destruction of the Russian military or even breakup of Russia? But does much smaller Ukraine, even serving as expendable proxies for the US, really have the ability to achieve that? And how would turning the Russian landmass into a power vacuum serve any but Chinese interests?
The US and EU never controlled events in Ukraine in any way, shape, or form. The Maidan revolt caught everyone by surprise, especially Putin. Nobody is urging Ukraine to fight Russia. Ukrainians are the ones refusing to surrender, not NATO. The US had even offered to get Zelensky safely out of the country when Russia broke the truce in 2022 and renewed its invasion. Zelensky refused, and the Ukrainian military surprised everyone by stopping the invasion almost in its tracks and repelling an attack on Kyiv itself. Ukraine could end the war by surrendering, but it refuses to do so. Putin could end the war by withdrawing Russian troops from Ukraine, but he refuses to do so. The only possible solution is a negotiated peace, but that cannot be done with Putin, because he is completely untrustworthy.
Finally, does anyone really believe that Russia will let itself be defeated without resorting to nuclear weapons?
They might still resort to tactical nukes, but most analysts seem to think that he won't. He probably would have used them already, if he were going to, because his military has been suffering defeats and is barely holding onto the territory that it has gained.