Its much more complicated than that.

Cancer is a group of diseases, some of them have vaccines now. But CIA had to use vaccination drives to look for bin laden, while knowing it will fuel anti-vaxxer movement. We can't let those terroist win.

We also know there isn't a single human alive that doesn't have microplastics in their blood. That's probably not good, (there are some research to suggest that it contributes to cancer). But plastics are a by product of petroleum, and lots of people will lose a lot of money if we stopped it.

Then also alcohol has a very strong connection with cancer. But lots of christians wouldn't like blood of jesus being demonized like that.

Then there is also research that suggest caloric deficit activates genes that fight cancer. But we must think of the shareholders, the marketing industry, and the global consumerist economy.

So you are kinda right, but also its waaaaaaaay more complicated/nuanced/messy.

Have you ever noticed how the more people learn about cancer the less they believe this? Usually a strong indicator...

Not so much.