Hypothesis. (can anyone corroborate?)

The root cause of anti-science, is the same as the root cause of:
Superstition
Conspiracism
Religion (generally)
Scientific Enquiry

... and it is this: humans hate uncertainty. We are biologically allergic to it. We simply loathe not being able to assume that the future is reliably predictable - the events that will transpire today and tomorrow are known with confidence.
Ancient humans invented magic, superstition and religion to try to control and/or predict the future.
Scientists throughout history have personally tried to understand the world, to be able to predict the future, because they were/are not comfortable with uncertainty.
Modern conspiracy theorists and anti-science-ists hate the intrinsic uncertainty of science - their mistake is that they judge science using black-or-white thinking. For them, science can never be good enough as a source of truth because science can never be 100% certain about anything - and yet that is precisely its power.

The difference between scientists and anti-scientists is, that scientists are comfortable with a little bit of uncertainty. They know that we can never fully 100% understand the world - but that's OK, as long as we understand it a lot - and as long as our understanding continues to grow. The Enlightenment in Europe starting in the 1600's was basically the birth and growth of a subculture of people who were a bit more comfortable with a bit of uncertainty - but who were keen to reduce how much uncertainty they had to put up with - by figuring out Nature and The World. The intention being - so that they can then predict the future with more certainty.

Anti-science-ists haven't learned - haven't understood - that uncertainty is OK We don't need to be 100% right all the time. We don't need to know absolutely 100% of something before we can be permitted to speak knowledgeably about it.