Diseconomies of scale and scope can prevent action in each of these industries, in a static analysis. It may prove to be more profitable to focus on a single industry (e.g. marijuana) than seeking at the present moment to dominate or even enter other industries (e.g. opiods) until market conditions change.
As things evolve, they may naturally enter other industries. Heck, even become legitimate.
EDIT: Fixed second paragraph.