The crux of it is the liberation from centralisation in Moscow which had previously laid down dictats about style. The architects of such experimental buildings did not become stars, they seem to have been genuinely experimental. But it is never architects alone, the client state has to lead the way by commissioning, enabling, paying for and promoting any kind of architecture for whatever reason.
That architecture is still taught as an idealistic discipline and then practiced as a pragmatic business is a slight problem here. Stars produce buildings as brands more often than as detailed investigations into accommodation. The epitome of this is Gehry's hubristic cloud in the Bois du Bolougne for Bernard Arnaud of LVMH, the ultimate brand-manufacturer, which has been stopped by what is in effect a community association for the care and welfare of the Bois, much, if the press is to be believed, to Gehry's fury.
What I find interesting about the Soviet buildings from Chaubin's book is that they are unknown to us, they are devoid of the language of late-capitalist modernism, and they seem fragile and optimistic. There is something quite cynical about the everyday architecture that I see, for example, filling up Calgary. It is repressive in a whole other way.