But you can just give computers to each of those millions of people and propagate the information, instead of having less reliable humans doing it? That's kind of what's already happening.
The problem isn't transmitting information, it's how the knowledge is created. Some information only exists in peoples head until they act on it. Sometimes they don't even know it themselves until they're forced to make a decision.
Problem of course is that a lot of this information is junk even at scale, which is how you get people "deciding" to pollute, destroy their own health, start wars, etc.