You may be looking at this backwards. It's not that congress is passionate about clamping down on compounding pharmacies and that coincidentally happens to help pharma. It's that pharma is starting to demand that the government get rid of obstacles to revenue maximization for their obesity drugs.
That forces us to ask ourselves what other major obstacles (beyond compounding pharmacies) would pharma be aware of and Tiktok influencers hawking gray market vials would be the next obvious target. They even telegraphed this to us by including "counterfeit" as part of the description for what they're targeting.
Really, we should be glad that they're taking this approach rather than figuring out a way to infiltrate seller supply chains and contaminate random gray market batches with fentanyl somehow, which is crazy to consider but is on the same level ethically as other shady stuff pharma has been caught doing before.