Most people are susceptible to scams like MLMs otherwise they wouldn't keep running the same scam. It doesn't mean you're smart or dumb, you just may not be aware of the social engineering and manipulation tactics they use or lack an effective skeptical epistemology to avoid accepting claims without good justification. Most people who are in a cult don't realize the organization they are in is a cult. I have an otherwise very intelligent sibling who fell for the essential oils MLM scam. They often use tactics and language similar to cults: in group/out group tribalism, indoctrination, isolation, love bombing, fear and hate mongering, etc.