You can pay for ads, videos, affiliates and launch campaigns to make people search for your course. If a cheap stolen copy appears during that search, the pirate may benefit from demand you paid to create.
The simple problem
You pay to get attention. The buyer compares options. A reseller offers your course cheaply. The customer may leave your real checkout.
What protection can do
Finding reseller pages, working on eligible search results and reporting commercial sellers can reduce the easy paths that lead buyers away from the official course.