We have these tiny little internal minds drowning in layers of external complexity, just trying to make sense of the limited peripheral vision that we have.
There is obviously a huge difference between “belief” and “degrees of belief”. By noticing these discrepancies, we are able to allocate levels of justification that cause us to test our own assumptions. There seem to only ever be varying degrees of knowledge rather than this one thing that we refer to by it.
Should we be shocked that people believe irrational things? Not really. We bombard children with information before we teach them how to think critically. It’s a daily mass murder of malleable mindsets.
Philosophers have pointed out since the beginning of philosophical thought that a high percentage of the justification value of our beliefs comes from how widespread the individual beliefs are. It’s as if our shared beliefs are characteristic of a virus.