Propaganda takes time. Often the most effective stuff happens when you aren't even aware of it. You progress through your regular life and encounter regular things. People bitch on the internet about stupid stuff with the occasional decent argument, and nothing looks out of the ordinary. You see laughable arguments about politicians with hints of truth, or intrude, but maybe you ignore it.

After a while you see more arguments along the same line of reasoning, but with more data and less vitriol. You find yourself agreeing more, even if you like the person being disparaged. You may even come around to accept a side of an argument you didn't think much about before.

This is how minds are turned. First the trolls and bots do as they do. Some people catch a whiff and continue the trend. Sometimes as a joke, other times seriously. Even those who pretend to be joking will not long be indistinguishable from the fools who think they are in good company.

Propaganda is not a tidal wave that comes crashing down on established opinions, it is a steady stream that eats at solid rock until it creates a deep gorge you could not have imagined structured in any other way.