Yeah, I vaguely recollected (again that podcast I linked) while their civilization was under siege by Cortes, they wondered why the gods had forsaken them. The whole thing is really tragic.

Edit: The wiki article states around 20k prisoners per year were captured for sacrifice, though perhaps the number might have been inflated to intimidate their enemies.

> Every Aztec warrior would have to provide at least one prisoner for sacrifice. All the male population was trained to be warriors, but only the few who succeeded in providing captives could become full-time members of the warrior elite. Accounts also state that several young warriors could unite to capture a single prisoner, which suggests that capturing prisoners for sacrifice was challenging

https://en.wikipedia.org/wiki/Human_sacrifice_in_Aztec_cultu...

> which suggests that capturing prisoners for sacrifice was challenging

Who knew... mortal combat was challenging?

The prisoner did not have to be a warrior or adult.

I don't know exactly of the aztecs, but in general the harder to get the sacrifice, the bigger the gods favour. So they probably wanted the biggest warriors, but took children as well, if possible.