CATO Institute has the following to say:
The U.S. government didn’t pay much attention to kratom until July 2013. That month, three advocacy groups sent a one-page letter to Daniel Fabricant, who was then the director of the FDA division that oversees the dietary supplement industry, which has annual revenues of $30 billion or more. The letter was co-signed by the heads of the United Natural Products Alliance, the Council for Responsible Nutrition, and the Consumer Healthcare Products Association, organizations representing dietary supplement producers and marketers such as Herbalife, Bayer, and Pfizer—but not, notably, any kratom vendors. “Given the widespread availability of kratom,” the letter said, “the dietary supplement industry is concerned about the potential dangers to consumers who may believe that they are consuming a safe, regulated product when they are not.” The organizations asked the FDA to “deter further marketing of kratom under the mistaken belief that it is a legitimate product.”
In other words, the U.S. government responded to complaints from competitors—not from consumers—in initiating its investigation of kratom.