Quick: Run a Google search for "Obamacare" or "Health Insurance" and see what the first listings which come up are. The odds are pretty high that the first listing won't be HealthCare.Gov, Pennie.com, CoveredCA.com or any of the other state-based ACA exchanges. In fact, the first link which comes up probably won't even be for Blue Cross Blue Shield, Molina or Centene (the actual health insurance carriers themselves).
It's far more likely that the most prominent sites to come up in Google's paid search listings will be third-party health insurance brokers. If you click on the link, you may be taken to a legitimate health insurance broker authorized to sell on-exchange ACA policies...or you may be taken to a fly-by-night quasi-legal outfit which either pushes junk plans or simply resells your contact info to fourth-party scammers. In many cases, they may even include the terms "Obamacare" or "ACA" baked into their names: