First of all, welcome
Second, I don't know whether your 'investigation' really is solid evidence. Mexico city is, behind Tokyo, the biggest city of the world. The number of hardstyle events in both North and South America is growing really fast, as is the popularity of hardstyle in general. The fact that the most likes are from Mexico city is therefore not solid proof of buying likes in my opinion.
As for the distribution of the number of likes, this may very well be positively related to bookings, releases or other stuff concerning the artist. Blutonium Boy got a lot of attention recently with his troll tracks, after a pretty long period of inactivity. And although I'm sure everyone here on this forum agrees that these tracks are absolutely horrible, I'm afraid that the 'new generation' of hardstyle listeners (who mainly know the popular names and have not, yet, deepened their sense of style) may actually not realise how horrible it is.
The fact that Theracords and TMS artists do not have a large fanbase in Mexico City could also simply mean that their music has not reached overseas yet, which is not strange since AFAIK none of them have actually performed there.
But, let me get 1 thing straight, I'm almost certain that some artists buy their likes as well. However, I don't think this kind of research is solid enough to serve as evidence; I'm afraid the only way to be certain would be if the artist admits doing this.