He states his thesis and then attempts to make the case intelligently. I disagree with the ultimate cause (advertising paradigm shift of 1950's or 1960's) but he's got the bases covered.
Incidentally, PEZ (pfefferminz) figured out marketing to children, rather than their parents, a long time ago. No one was buying the after-cigarette mints and the makers observed that here, in the USA, children had the unique power of dictating purchases to their parents. Elsewhere in the world the children did as they were told and did not overstep this boundary. In the US there were kids whining and begging for trinkets and candy everywhere. So the makers of this unsuccessful after-cigarette mint decided to glue toys to the top of the mint dispenser and sell them to kids. Now PEZ, destined to fail in the 1920's, has lasted almost a century.