An entire ideological framework of cold war vanished together with Soviet Union and communism.
However, imho it looks like during 90's Nato and U.S chose to ignore the facr there is still a super power there, buried underneath the ruins of Soviet Union. And this super power, once finished with putting it's shit together, will have it's own interests and needs in the area, still.
From today's NYTimes, it seems the decision to ignore Russia was a gesture in appreciation of Boris Yeltsin:
"As a gesture to the Russia of Boris Yeltsin, who grudgingly accepted NATO expansion, ?NATO never developed military plans to defend central and eastern Europeans, because we said, ?Russia?s not an enemy and not a threat,? and we never backed up the new members with exercises and infrastructure,? said Mr. Asmus, who was a senior State Department official in the Clinton administration."
I guess we (US govt) forgot to update our little black book when Putin came to power
Ending up surrounded by countries that either sleep together with U.S or even belong to Nato IS NOT Among Russia's interests. Through 90's they were a complete mess and Nato as able to do as they please in the region. Now, about 20 years after death of Soviet Union Russia is finally feeling functional enough and influental enough to do something about Nato(quite ruthelessly) expanding to what is their turf.
It's about sending a message to countries in the region. "Check the map guys. remember what you have next door. Stop flirting with Nato."
yes, from Russia's POV, it makes sense to prevent this exodus of former Soviet blocs and neighboring regions into an organization whose original purpose was to be anti-Russia among other things. From the same NYT article:
"The Orange Revolution in Ukraine, which Russia failed to stop, ?was the real wake-up call for Putin,? Mr. Rupnik said. ?The Russian conclusion then, and it?s widely shared there, is that the limit has been reached ? no more concessions, a push for rollback, and definitely no Georgia and no Ukraine in NATO.?
Another interesting point it makes is about how France, Germany and Italy are dependent on Russian oil/energy, so they are not willing to be outright hostile to Russia (like relation between the US and Saudi Arabia). Which leaves the US to prop up NATO?