Rising use, low production costs and logistical advantages could eventually lead drug producers to focus on fentanyl instead of cocaine, a high-ranking Colombian police official said, but for now cocaine remains that country's top drug export.
I'm surprised they are competing with each other, being very different substances with very different effects, and I wouldn't think their user bases overlap much.
At that level buyers & sellers are likely drug agnostic. They buy whatever sells & sell whatever is being bought. Profit margins are likely what's driving the transition. However, & somewhat to your point, why not both?