In the LRB, James Meek suggests that support for pan-Russianism is helped by generational change:

Many of the most articulate and thoughtful Russians and Ukrainians, those of middle age who knew the realities of Soviet life and later prospered in the post-Soviet world, have moved abroad, gone into a small business or been intimidated: in any case they have been taken out of the political arena.
In Russia and Russophone Ukraine the stage is left to neo-Soviet populists who propagate the false notion of the USSR as a paradisiac Russian-speaking commonwealth, benignly ruled from Moscow...If you were born after 1985 you have no remembered reality to measure against this false vision.

This hints at an interesting mechanism in the social sciences - that change can happen simply as one generation forgets what an earlier one knew. As George Santayana said, "Those who cannot remember the past are condemned to repeat it."

My favourite example of this is Andrew Newell's explanation of why the inflation/unemployment trade-off worsened in the late 60s. It was, he says, because a generation of workers who remembered the depression of the 1930s retired and were replaced by a generation that had known nothing but security and full employment and so were more emboldened to push for higher wages.

The same could be true in financial markets. It's sometimes said - in a variation on Minsky's financial instability hypothesis - that stock market bubbles occur after a generation that remembered previous crashes has retired; given short careers in the City, this happens quite often.

It's possible that a similar thing happens in attitudes to wars. It might be that the US and UK became keener on overseas adventures as memories of Vietnam and Suez faded.

The psychology behind this is Humean. Our actual lived experience gives us impressions which enter our mind with "force and violence." But the experiences of our parents and grandparents which we only hear or read about are mere ideas, which are only faint images of impressions.

So far, so good. But this is only half the story. It is also possible for the experiences even of distant generations to affect our behaviour now. For example, Germany's experience of hyper-inflation in the 1920s makes them inflation nutters today; Greeks' experience of Ottoman rule has made them disinclined to pay tax; and slavery has had a long-lasting economic and perhaps psychological impact.

Sometimes, then, historical memories fade and sometimes they linger - in both cases with material consequences.

This is not a contradiction. What we have here are two separate mechanisms through which history can cause social change - in one case because it's forgotten, in another because it's remembered if only viscerally. All of which vindicates Jon Elster:

It is sometimes said that the opposite of a profound truth is another profound truth. The social sciences offer a number of illustrations of this profound truth. They can isolate tendencies, propensities and mechanisms and show that they have implications for behaviour that are often surprising and counter-intuitive. What they are are more rarely able to do is to state necessary and sufficient conditions under which the various mechanisms are switched on. (Nuts and Bolts for the Social Sciences, p9)