Knowledge is everywhere. We can investigate, reverse engineer, research, ask for, and look up things we want to know. The line between which information is inside an individual's head and which is outside is blurry. Opportunities for ignorance abound. A typical human brain carries roughly 1GB of memory. That is equivalent to about 500 photos, though a cerebellum is clearly different than digital hardware. The mind evolved to help organisms act. And correct action is more important than correct understanding.
Social collaborations allow people to exchange information such that the whole of society is greater than the sum of its parts. Technology is integrated into our lives. Because we have access to answers, we are regularly tempted to assume that we are experts. Those assumptions are rarely tested. Beliefs are inherited through culture. In the political arena, feelings often feel like they are facts. Adults stop questioning things and people almost never enjoy having their illusions shattered.