Some of it was that thiccer women weren't available in the industry, but also this video basically started a trend that become more extreme and exaggerated over the last 3 decades.

Slim thic women who have those features naturally became more marketable. Women who naturally have more extreme versions of those features were able to exploit them so then people who wanted to make money off those features started selling them and eventually you hit the BBL era which is the trend started here to the nth degree.

But back then he would have been largely referring to women in the size 10/12/14 range (not fat or skinny) that had features her preferred since Hollywood at the time was largely using size 2/4/6 women for magazines and modeling.

The easiest comparison is to look at the Victoria Secret's models of that time.