Twelve year olds are fucking stupid. You think teenagers are stupid, getting peer pressured into sex because they want to fit in or doing stupid shit because their friends are? Teenagers are megamind compared to twelve year olds. All it takes is older members of the group to start talking about how, oh, this character is so cute - these two would be so cute together, and wow, look at this cool (but risque) fanart I found/drew! Grooming is a game of slow escalation. You're dumping kids in a pot of water you slowly turn up until they think sending nudes to people ten years older than them is acceptable and making jokes about dick sucking in front of ten years old is funny because it's not a big deal.