Ritual sacrifice, including of children is well documented all across the world (https://en.wikipedia.org/wiki/Child_sacrifice). So it's not a question of likelihood, we've dug up plenty of gravesites documenting it especially in Mesoamerica. There's even some modern examples, with an isolated tribe of Chilean natives sacrificing a 5 year old after the 1960 Valdivia earthquake.

You have it sort of backwards. These practices are only 'horror' by modern standards, it doesn't make sense to disregard history because we live by other values than an ancient civilization.