It was the lack of access to the right information. Most people won't spend hours researching a topic. Most people don't spend any time on seeking outbinformation. They only absorb whatever information they happen to come across. And liars are especially adept at being loud. So they're the first, and often only, to be heard.

In a world without corruption, a ministry of truth would work wonders. In our world, I don't know what would work.