"I'm not sure I can get behind that definition. We can't trust Merriam-Webster as it has been compromised."
I find that statement somewhat disingenuous. After all, a conspiracy theory is obviously a theory about a conspiracy. You hardly need a dictionary to define it.

As for the fear factor:
While fear might be associated with a conspiracy theory as it could be with just about anything else e.g. a doughnut.
Yet there's no way that fear would be would be cited as being one of the primary defining charistics of a doughnut.
The same applies to conspiracy theories.
Also, a conspiracy theory doesn't nessarily involve "a Government"