Diplomacy was tried and didn't work.
This isn't to say that Ukraine can't defend itself from Russia, or that the invasion was good, but a simple recognition that there were things that led to this situation that were unforced.
The point of NATO has been said to "Keep the Americans in, the Germans down, and the Soviets out" [of Europe]. Post-1991, there is no need for it and it has mainly been used to provoke and bomb other countries such as Afghanistan, Iraq, Libya, Yugoslavia, and now Ukraine/Russia. Arms manufacturers are kissing their freshly printed dollar bills and thanking our economic system for their great fortune.
Russia requested that nato would leave all the eastern european countries that had joined, Poland, Baltics, Czechia, etc. Then russia could also start invading us after it had taken Ukraine.
Russia was mot interested in diplomacy, they just wanted Ukraine one way or other.
1. There was no 2014 coup in Ukraine, there was a change in president (ratified by parliament) because the first guy (Putin's stooge) had the police kill protestors. This predictably provoked riots, but a riot isn't a coup and indeed the government wasn't overthrown.
2. The invasion was never about NATO; this was just one in a litany of obvious propagandist justifications and it has no more credibility than any of the others ("de-Nazifying Ukraine" and "defending ethnic Russians against genocide"). To wit, if Russia was genuinely motivated by NATO encroachment why would he, after years of NATO weapons, personnel, and doctrine being turned away from Russia and toward the middle east, would it do the very fucking thing designed to flood Russia's doorstep with NATO weapons, personnel, and member states?
3. The idea that there has been no need for NATO since 1991 (because Russia hasn't been particularly aggressive) is a non-sequitur--Russia hasn't been particularly aggressive since 1991 because of NATO.
4. NATO has not been used to provoke conflicts with anyone.
5. NATO didn't provoke an attack in Afghanistan; Afghanistan aided and abetted an attack on a NATO member state. Recall NATO is a defensive alliance.
6. NATO wasn't involved in Iraq; various member states were involved.
7. NATO bombing in Libya was implementing a UN Security Council resolution (recall that China and Russia have UNSC veto rights which they declined to exercise).
8. NATO did intervene to halt an ethnic cleansing campaign in Yugoslavia. They found a loophole in International Law that allowed them to intervene legally.
9. NATO had no role in the Ukraine/Russia conflict except to provide Ukraine with the weapons, training, intelligence, etc necessary to defend itself. Russia is the unambiguous aggressor.
10. "The point of NATO has been said to..." this is not evidence, it's baseless rhetoric. I promise