Sacrifices always seem to be presented as the killer or the people giving up something they value, but I would not be at all surprised if it were basically a display of power — killing people those who are poorly-connected or who are rivals in some way.
"Those young victims, most likely a girl and a boy roughly 4 to 8 years old, drank a liquid that may have lightened their moods and calmed their nerves in the days or weeks before they were ceremonially killed and buried on Peru’s Ampato mountain, a new study suggests."