Let's say I am a guy who manufactures pharma products around a hundred or so years ago. I made decent money but people are generally healthy. After some time, I figured out that curing people was not as profitable as treating just the symptoms and so I modified my products to address the symptoms but do nothing to fix the thing causing the symptoms.
Then later, I figured out that I could inject people with a, "vaccine," to, "prevent," them from getting something they may not get anyway, sort of like insurance. I also figured out that I could in fact infect the people with the very thing I said I was trying to, "protect," them from.
More symptoms, no cures, actually causing the spread = $$$
Then I figured out I could cause my so called, "medicine," to create more symptoms that would require more of my products to address and on and on.
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$