“What actually happened is that, as part of the deal to reunify Germany, Russia had been given assurances that NATO would not be expanded in its direction - assurances that were then repeatedly broken.”
Russia was never promised that NATO would not expand beyond a unified Germany.
http://www.nato.int/docu/review/2014/russia-ukraine-nato-crisis/nato-enlargement-russia/en/index.htm
As for the possibility of NATO membership for Russia, there have been both back-channel discussions and very public expressions of interest, the latter going back to Molotov in 1954.
NATO is hardly an uninterested party in the dispute.
This is plain common sense. When the Cold War ended, the need for a military alliance against a no-longer-in-existence USSR ended with it.
To then expand the alliance to the borders of Russia is nonsensical, UNLESS the intent is to make enemies of them again. Without such intent there is no reason to expand the organization.
The only way to not see this is to be completely unable to put oneself in another person’s shoes. How could Russia possibly see NATO expansion as benign, especially in the wake of the war in Yugoslavia, and the later war in Iraq?
And then Libya, and Syria, and Ukraine... the US has been systematically overthrowing governments friendly to Russia.
If we were in their shoes, the need to act in self-defense against the growing threat of US aggression would be so obvious that anyone who didn’t see it would be regarded as crazy or suicidal.