I think the article makes a good case for it having more to do with a kind of cultural globalization among financial elites than with QE, since the market has been booming more less continuously since the 90s and not just since 2008/9.

"Since the doldrums of the early nineties, the market for contemporary art, which has various definitions (work created after the Second World War, or during “our” lifetime, or post-1960, or post-1970), has rocketed up, year after year, flattening out briefly amid the financial crisis and global recession of 2008-09, before resuming its climb. Big annual returns have attracted more people to buying art, which has raised prices further. It is no coincidence that this steep rise, in recent decades, coincides with the increasing financialization of the world economy. The accumulation of greater wealth in the hands of a smaller percentage of the world’s population has created immense fortunes with a limitless capacity to pursue a limited supply of art work. The globalization of the art market—the interest in contemporary art among newly wealthy Asians, Latin Americans, Arabs, and Russians—has furnished it with scores of new buyers, and perhaps fresh supplies of greater fools."