The painting is also famous because it is famous. I once read about this effect in an article about a music website for breaking new artists by voting for them. Say there were 10 new songs that were all equally good. You would not see an equal distribution of votes. What happens is, one song starts getting votes and that makes visitors notice it more so they wind up voting for it which leads to others noticing it and voting for it and on and on. Eventually one song winds up way ahead of all the others, so you would think, oh, that is clearly the very best song. But it's not really, they are all the same goodness.