It's also because Mexicans are midgets so can naturally flood the lower ranks with their fighters. Contributing factors. (braced for impact)
Nothing wrong with it, just that your average mexican is a lot more likely to be able to compete in those divisions than your average American or European. Hence why they are dominant down there yet almost non existant at the top of the larger divisions. I'm not disagreeing that their ****ing hardarses either. Just giving some reasons other than 'omg I love mexico and would like to suck some mexican **** because mexicans are obviously a superior fighting race...' that seems to be the main spirit of this thread.