It's really simple and I'm surprised you question this being a leaf, wouldn't be surprised if you were a mutt asking this question. But since their ancestors were from Spain I'll answer you on their behalf.

Instead of killing them all, we allied with some tribes due to our lack of manpower, after that we had to keep them. We converted them into christianity because well, they had human sacrifices and shit and that was not really acceptable in the reinassance you know. So well, their spaniard ancestors settled down and started to mix with them, but ultimately the brown gene overshadowed the white. They're literal apes, midgets, same faces, violent, low IQ.

If we had done the same as the brits... I think you would speak spanish today, but oh well...