I feel like this phenomenon is over stated a lot. Usually I hear things like people stop maturing the age they become famous but honestly there are far more Mara Wilsons and Sean Astins than Corey Feldmans and Amanda Bynes.

We even force narratives to suit this. I remember pictures of Macauley Culkin going around. That was a guy who admits his childhood was pretty fucked up and he mostly just kept to himself afterwards and dropped out of the public view. But when pictures of him looking a bit skinny and with long hair came out everyone was claiming he was on meth. For no real reason. Culkin and his brothers have never been big or broad people and Macauley himself has had on and off again long hair since he was a teen. But people wanted the narrative of messed up child star.