However, if Russia conquers Ukraine, Russia will be more powerful and threaten the West.

This oversimplification of this conflict is the root of the problem. "Russia conquers Ukraine" is not remotely what's going on. "Ukraine" is yet another of the innumerable examples throughout history of political borders which do not accurately reflect the tribal reality that exists on the ground. The people in the west of Ukraine HATE the people in the east of Ukraine and vice versa. These are two mutually antagonistic tribes. The group from western Ukraine took power in 2014 from a leader who had been aligned with the eastern Ukrainian faction. The eastern Ukrainians are majority ethnic Russians (overwhelming ethnic Russian in the case of Crimea), and those ethnic Russians never accepted that transfer of power. The links between this population of Russians in Ukraine and Russians within Russia's pre-2022 borders are family links, ultra-tight. There is no Russian government that could ever ignore persecution of Russians in Ukraine or the potential that Ukraine become a sworn enemy of Russia (the baseline meaning of "joining NATO"). This is so far beyond "Vladimir Putin" as to be laughable. Russian governments going back to Gorbachev (the "western hero") have been absolutely clear on this point for decades. Ukraine CANNOT be aligned against Russia. This is existential for Russians and always has been. Zip, zilch, zero to do with Putin. No leader could claim to be Russian and take the opposing point of view.

Russia does not want to "conquer" Ukraine. Russia wants two things: first, they have made formal what has been de-facto true for longer than anyone living today remembers - i.e. the eastern provinces, being ethnic Russian and being unwilling to be ruled by a separate ethnic group based in western Ukraine, are indeed Russians. That's what the annexation of the Donbass represents. Second, western Ukraine - which is not Russian and cannot be Russian - cannot be used as a forward military base for NATO to stage hostilities against Russia. Russia has been invaded from Europe multiple times in its history (anyone remember Napoleon? WWII anyone?). Again, this is way beyond the whims of Vladimir Putin; it is deep inside the Russian national character. Ukraine not being in NATO is something the Russians are willing to fight a war over.

Russia does not want to "conquer" Ukraine. They are fighting this war because they will not offer anyone again the opportunity to invade them from the west, as long as they can help it.

The takeover of the Ukrainian state by the western faction in 2014 was a tripwire. The resulting response from Russia was ironically surprising only in that it took longer than many of us would have expected for Russia to respond emphatically. The restraint shown by Putin from 2014 to 2022 was a measure of his desperate hope that Russia would be able to form a normal trading relationship with Europe and avoid having to take the bait offered by NATO of direct conflict.

Putin is not a saint. He's the leader of a state in Russia, and Russian politics has always been highly centralized and very corrupt. He's no different. But that is actually utterly irrelevant to the dynamics I have just described. The leadership in western Ukraine is absolutely the match (and then even a little more) for corruption, venality and ignorance as anything the Russians can put forth. Of course they are. So both regimes are thoroughly corrupt. But this war is way beyond that, and the profound misunderstanding on the part of the west of the motivations of Russia here (not just Putin, RUSSIA) is central to the understanding of why more than half a million men are now dead on both sides of the line in Ukraine.

It's a tragedy of human ignorance - on both sides, and to say "It's Russia's fault!" is the perfect embodiment of that ignorance.