It was primarily the lumber industry that is responsible for marijuana being illegal. They put pressure on politicians who needed money and newspaper owners (can't print a newspaper without paper). Politicians also needed the support of the newspapers to get elected which they wouldn't get with the lumber industry pulling the strings. Marijunana was also used by a significant number of migrant farm workers who were mostly black and latino that couldn't afford to buy bootleg whiskey so it provided another excuse to the largely racist public and gave white law enforcement an excuse to hassle minorities during prohibition redirecting the focus from bootleggers(who were white).