What a neat idea! I tend to lean towards more grounded stories myself. Along similar lines, like the Aztecs, the fluffies of the woods engage in these blood rituals and find the placebo effect of their actions the necessary boon to push through the hardships they face.
The animals that profit off of this are just in it for the oddly regular freebies, much like how stray animals that people feed will return to them routinely.
Until, of course, there’s the one that is not content with such an arrangement and wipes out families to sate its particular needs at the time.
But the rest of the population assumes that these events are just the ritual eliminating competing smarties and that their respective smarty will be the one to prevail.
They all think everything is working in their favor. All of them, up until the select few face their inevitable swift dooms.
I didn’t mean for this to be a metaphor for Mesoamerica vs the Conquistadors but here we are.