The critic doesn't make an argument, just states a claim for which we need to find support. The claim is that audiences are reasonable to prefer hearing more famous concert pianists play, and this preference should not make us doubt audiences' ability to judge the quality of the playing. We can extrapolate from this that some cynics might claim that audiences only care about these pianists being famous, and aren't actually paying attention to the quality of their musical skill. The critic's claim denies this viewpoint.

The critic's reasoning can be seen in the phenomenon-hypothesis framework. The critic observes a correlation between pianists' fame and audiences' enjoyment (the phenomenon), and, despite not directly posing a hypothesis, clearly favors an explanation that gives credit to audiences' ability to judge the quality of music. So the critic is almost implicitly hypothesizing that high-quality piano playing goes along with the pianist's fame.

For this reason, we can support the critic's claim by showing that good playing correlates with the fame of the pianist. That would justify the critic's statement by telling us that audiences do actually most enjoy the best pianists, who just happen to also be the most famous.