I don't know. To me, calling something a "conspiracy theory" is a way of dismissing it, without digging too deep into the substance. Sometimes appropriate, sometimes...not so much.
My guess is that "conspiracy theories," like "radical ideas" and/or "crazy notions," simply fall well outside the parameters of whatever is considered "normal." I'm not into conspiracy theories myself, but I do get somewhat uncomfortable when unpopular ideas (and people...) are quickly dismissed and labeled. Kind of like...Goldwater was psychoanalyzed by the shirnks in '64, so now the shrinks have the "Goldwater Rule," where they're not supposed to be label politicians, but...Trump is polling in the low 30s, so lots of talking head shrinks are labeling him, anyway, just as they did Obama and...on and on it goes. Point there is that the labels they slap on Trump and others are basically to shut them up and dismiss and invalidate them, which is what calling an unpopular idea a "conspiracy theory" is all about, too.