I would be curious to see how historically accurate the rape claims are. Explorers often misunderstood the context and what they viewed as rape might have simply been part of the sacrificial process, or otherwise exaggerated. Not to say this was the case, but it would be interesting to see how close the stories get to the archaeological record.

Mass rape followed by mass murder was kind of standard for most early civilizations in war before the invention of slavery. At which point it became mass rape followed by mass slavery. So I'm not sure why the rape would surprise you.

The temple guards where sick little fucks who whole only job was to drug the victims and make sure they didn't run away before being led to the top the tower one at a time. Raping the victims wasn't part of their jobs but when you're a mass murdering prison guard doing a boring job then rape isn't a big step.

It pissed the priests off but it was hard to stop. The account about rape comes from the Aztec priests themselves as recorded by Spanish chroniclers after the conquest.