In this case where profitable traders get in newbies to teach trading, their aim isn't only on the money that they would earn from teaching their students trading, but their target is getting those students to register via their referral links and they will earn passively in as much as those people continues to regardless of weather they lose or profit and the more people they get on board via their referral links, the more money they will earn passively.
You are absolutely correct, I missed the fact that these people who open courses are affiliated with broker company, and sometimes they got exclusive contract from the company. Nevertheless, I will always remind people who trust blindly to these so-called trading masters, that they are actually have became a product to them once the signed up to their course, that these people might not as good as what they claim.