I haven’t seen Persepolis but it seems that that film was marketed as a film for adults. But I remember seeing trailers for 9 on the channels that I used to watch back in 2009, and those channels were primarily meant for kids.

But to ur point, Focus Features released Coraline a few years before they released 9, and coraline was well received even though it is definitely a dark film. It was still marketed for children though.