> It's an old strategy. It's commonly been part of plots of various stories/movies in the US going back decades.

I think significant aspects of it are quite novel – e.g. teenagers being recruited via Signal or Telegram, often by overseas fugitive gang leaders; some cases have even (allegedly) involved Iranian government agents

Also, there's a difference between something repeatedly happening in fiction over decades, and law enforcement seeing multiple real life cases of it over a few months in a single metro area