To be fair to Mill he made a wide set of contributions to political philosophy and ethics outside of his work on utilitarianism as well as some influential work on the philosophy of science and logic. Not to mention he made several contributions to economics and was, to his credit, also a proto-feminist.
So, I hope this might explain why those who work on inductive logic, philosophy of science, and perhaps even a feminist or two would vote for him over Nietzsche. So it's not just a bunch of smelly utilitarians. Although I am a bit surprised Nietzsche lost as well and am not sure who I would vote for.