Well, being talking about SPANISH-speaking countries, most of them prefer a lot salsa, cumbia, merengue, bachata and other "latin rhytms" than "metal music"... So i am not so sure that there is some kind of correlation between "number of metal bands" with other GDP or financial or even development or cultural variables.

I would say that this data simply show us in which countries there are preference to Heavy Metal, compared with other countries in the "spanish-language cultural sphere". Without any other conclusion or interest. Do you not agree with this statement?

Anyway, u/metalstats is right: is very easy to have quite exact stats about metal bands thanks to the incredible free project of https://www.metal-archives.com/ but it is quite difficult to get the same info regarding other musical genres. At least i don't know where to get it.