The patent is not exactly on the compounds (or meant to make cbd exclusive or restricted to being a government product), it’s for a method to treat severe oxidative stress in the brain (such as what is seen clinically following stroke or heart attack), the compounds that they are using for this purpose are cannabinoids. The structures of the major cannabinoids were determined between the 30s to the 60s - that means the compounds are not new inventions and can’t be subject to being patented as an invention in what you linked (filed in the late 90s and granted in early 2000s). This is unlike other newly discovered drugs (synthetic or natural) that can be patented because they were previously not known. You can however patent a new unexpected use of some old compound, in this case protecting the brain following a stroke or a heart attack. In fact that is a way that companies have tried to keep their drug patent “evergreen” and extend their exclusivity, get it approved for new applications. Now, why is the process of getting a patent important, and not necessarily a bad thing? Because if you want a drug to be recognized and approved by the FDA and therefore administered by legitimate medical professionals with confidence to their patients, it needs to get patented for a specific use. Physicians can still prescribe things “off label” but it’s a physician and consumer confidence thing that a drug gets FDA approved for specific uses where it shows effectiveness as proven by rigorous, documented testing.