Why do you say he's that much more popular? I don't think it is accurate. What you will get a lot of outside MTF are people that's heard of Nadal but won't recognize the name Dimitrov. In here that is not an issue, everyone has heard of both. And among those that know both, popularity is much more evenly divided than you suggest.
True. This is a tennis forum. More than the top players who get more exposure, magazine spreads etc. get recognized