At high school I heard a presentation how cannabis was criminalized by cotton farmers to kill hemp farming.I still fon't know if it's yrue or some pot head conspiracy theory. This gives it a bit credibility, though. https://www.theguardian.com/world/2021/jun/05/turkey-experiments-with-cannabis-crops-to-boost-hemp-production
Wikipedia notes "Interested parties note the aim of the Act was to reduce the hemp industry through excessive taxation largely as an effort of businessmen Andrew Mellon, Randolph Hearst, and the Du Pont family." https://en.wikipedia.org/wiki/Marihuana_Tax_Act_of_1937 "Interested parties" may still be potheads.