It's quite strange how people's self-objectification varies so much

I've seen a doctor who graduated from medical school and earns 300 million KRW annually after tax, yet claims they aren't that smart.
On the other hand, I've seen someone who only finished high school, runs a small business, and is drowning in debt, yet insists they were born with a brilliant mind.
While the criteria for what defines "intelligence" might differ from person to person,
it seems that their level of self-confidence is entirely separate from the objective standards held by society.