This type of faulty reasoning also frequently takes the form of affirming the consequent: https://en.wikipedia.org/wiki/Affirming_the_consequent

(P→Q,Q)→P

It happens often when people have a limited consideration set of possible causes, often due to a natural degree of ignorance or lack of experience relating to the subject matter area, e.g., a small child sees a wet sidewalk and assumes it rained, because they aren't yet aware of sprinklers (or garden hoses, etc.)

(If rain→wet sidewalk, wet sidewalk)→rain

The title alone might be clumsily restated as:

(If amateur endurance athlete→rich, rich)→amateur endurance athlete

Sticking my frequentist nose in here, this is maybe better described as the Base Rate Fallacy: https://en.m.wikipedia.org/wiki/Base_rate_fallacy

Nice, thanks! Though that page mentions and uses Bayes' Theorem a lot ;)

Thank you! I knew it had to do with Bayes' theorem. So much confusion in the world seems to come from the fact that people don't understand conditional probability.

The error has a name! I never knew! I just tell my students "you can't flip conditional probabilities like that."