So recently, governments have been using 'conspiracy theorist' to attack basically anyone who does not accept government narratives. If you don't believe in their good will and morality, you are a conspiracy theorist. In fact, a local paper once claimed that people who believe that politicians are corrupt, or that the media is pushing an agenda, are conspiracy theorists. So much for that.
It doesn't matter if it actually involves a conspiracy or not. For example, if you believe that 9/11 was an inside job, then you are a conspiracy theorist. However, if you believe that the Nord Stream sabotage was NOT an inside job, you are a conspiracy theorist. The only thing those two have in common is that you are not a conspiracy theorist if you say the US government did nothing wrong.
Regardless of the double standards, the problem is the conspiracies do happen. Now, what actually is a conspiracy theorist? Because there are a good number of totally whacked people out there, who believe in wildly implausible conspiracies.
My best way to explain it is as follows: people who exclusively or preferentially explain things with 'conspiracies' are conspiracy theorists.
As a denizen of the shitposting internet of the 2000s, I've had to explain to a large number of people that "theory", such as "theory of evolution", means "established current knowledge", not "wild mass guessing".
Expanding on this, theorist would be one who works with theories, with established and not-yet-unproven truths.
A conspiracy is two or more people communication with an aim to perform some action that is, traditionally, viewed as immoral or unlawful.
Therefore, a conspiracy theorist is a person who specializes in the established current knowledge and not-yet-unproven fact-state that people exist who are working together to perform some action that is immoral or unlawful.
In example, someone who says the Ford Pinto was purposefully designed to save money despite the execs knowing it would kill thousands of people? Conspiracy theorist. Someone saying ENRON did not report their financial situation with material accuracy? Conspiracy theorist.