It's only when a subject becomes popular that the propaganda gets recognized and rectified.
* A sketchy online university that was clearly manipulating their Wikipedia page with lots of positive information about themselves to suppress info about their active lawsuits and controversies
* On medical topics: non scientific, baseless claims about the efficacy of various herbal treatments, vitamin supplements, or other snake oil treatments.
* On various fringe politicians. Someone clearly rewrites the article or adds additional things to the article with claims about what the politician has done or not done or wants to do, but these claims are arguably not fact based.
Now these things usually don't last for a long time. They do get rolled back or removed. But it doesn't have to be on there long for it to be utilized. For example, someone just needs to modify the Wikipedia page long enough to get through their active lawsuits, or the snake oil salesman just needs their info up on Wikipedia for long enough to use it to increase their perceived authenticity to trick some seniors. There is such a constant stream of bad actors trying to put this stuff out there that you'll see it eventually, and it doesn't even have to be up there for long for it to be harmful.