They are all around us and have always been around us. I don’t believe them.
There have been conspiracy theories about every branch of government and about “big business”. Theories about who assassinated JFK, Lincoln, etc. Also about how business and government work together to make the “common” man suffer.
My statement: The more complex, and more assumptions a theory makes, the less likely it is to be true. Of two theories, the simpler one is more likely to be correct. Also a theory has more validity if it requires less exterior support, and if it does not contradict generally accepted principles. The less it involves, the better.