I think cow clicker had novelty and the empty room psych on its side as well. Humans tend to obsess upon things which seem to have a purpose but no obvious one. Nobody bats an eye at the same tree used hundreds of times of a plot important but a single beggar with grey rags instead of brown? They must be more important somehow!

Well before then players of the original Diablo were obsessively clicking cows because of rumors and belief that there had to be something to the cow.