The model of knowns and unknowns.

Known knowns are facts that you know. Known unknowns are facts that you are certain you don't know. Unknown unknowns are facts that you don't even know exist.

Unknown known is fact that you do not know but others do. Also the most fertile ground of conspiracy theories.

When you are ignorant of something you get a free pass to make up any fact and attribute that knowledge to someone else who is in the know of it.

Here is the issue -

There are more people who are not well versed with even the most basic things. Not to mention, what could be considered basic has been widening rapidly.

The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts. ~ Bertrand Russell

The worst thing that the internet has done is allowed for the broadcast of such thoughts to a wider and wider audience without the fear of any repercussion.

The weapon of choice for such people is stories. Stories are used to establish these conspiracies. Stories are far more certain than any data can ever be. They will look at the pictures of astronauts on the moon and argue that there are no stars in the background, conveniently ignoring the fact that they don't see stars during the day on earth either.

The Unknown known gives people the ability to make assumptions about the things others know and concoct whatever theories that suit their fancy.