"addiction in children’s brains"
I don't think these corporations deliberately aimed their content at any age group. Kids are not ready for alcohol or cars or pron. Did the corporations care? Probably not. Would they have at one time, here in the US? Yes, back when legislators were answerable to their constituents. At one time the FCC worried about the lyrics in songs on the radio. The population was more uptight about it. Then.
OTOH: I recall times when parents oversaw what their children consumed. They didn't need to buy them smartphones or laptops, and they could have enforced rulse on their use. Parenting isn't for everyone.