When to believe conspiracy theory?

It's a tough one because rich and powerful people do act to seve their own interests, often in covert ways. However, that doesn't mean that any BS read from a dodgy website happens to be true. You need concrete proof to say something definite. To see something as even credible, I think there are three questions to consider before saying it might be true:

1) Would rich and powerful people benefit? (not just the one's I don't like)
2) Does it have a credible narrative.
3) Would it be worth the risk of exposure.

For example I never believed the 9-11 truther stuff because of number 3. All three are a yes to Iraq WMD. Pizzagate fails on every count, as does Cultural Marxism.