Things went south probably before that. Here's a short insight form George Kennan, from his 1998 interview regarding Senate's approval of NATO expansion:

...
 ''I think it is the beginning of a new cold war,'' said Mr. Kennan from his Princeton home. ''I think the Russians will gradually react quite adversely and it will affect their policies. I think it is a tragic mistake. There was no reason for this whatsoever. No one was threatening anybody else. This expansion would make the Founding Fathers of this country turn over in their graves. We have signed up to protect a whole series of countries, even though we have neither the resources nor the intention to do so in any serious way. [NATO expansion] was simply a light-hearted action by a Senate that has no real interest in foreign affairs.''

''What bothers me is how superficial and ill informed the whole Senate debate was,'' added Mr. Kennan, who was present at the creation of NATO and whose anonymous 1947 article in the journal Foreign Affairs, signed ''X,'' defined America's cold-war containment policy for 40 years. ''I was particularly bothered by the references to Russia as a country dying to attack Western Europe. Don't people understand? Our differences in the cold war were with the Soviet Communist regime. And now we are turning our backs on the very people who mounted the greatest bloodless revolution in history to remove that Soviet regime.
...
''It shows so little understanding of Russian history and Soviet history. Of course there is going to be a bad reaction from Russia, and then [the NATO expanders] will say that we always told you that is how the Russians are -- but this is just wrong.''
...

http://www.nytimes.com/1998/05/02/opinion/foreign-affairs-now-a-word-from-x.html

With or without Putin Kremlin would see this as a fundamental security problem for Russia. Those who do not share such a view in Russia have a public support in the order of a statistical error.

Whether that POV is fundamentally right, or is a mixed bag of misconceptions, fears, and some objective truth etc, is beyond the point. It is one of the few pillars of Russia's strategic culture and it must be taken seriously.