I think I am smarter than everyone around me, why? Am I smart or am I an idiot? Is it because I underestimate people?

Oh, welcome to the club!

I don’t know who you are but given the details added to the question, I would recommend you to check this quick Wikipedia entry:

Dunning–Kruger effect – Wikipedia

In short:

“The Dunning–Kruger effectis a cognitive bias in which low-ability individuals suffer from illusory superiority, mistakenly assessing their ability as much higher than it really is. Dunning and Kruger attributed this bias to a metacognitive incapacity, on the part of those with low ability, to recognize their ineptitude and evaluate their competence accurately. Their research also suggests corollaries: high-ability individuals may underestimate their relative competence and may erroneously assume that tasks which are easy for them are also easy for others.”

What is the single best financial move you have ever made in your life?

My single best financial move was when in 2008 (just before the Financial Crisis) I decided to invest every month a certain amount of my salary in a moderately risky ETF like Vanguard’s VOO or VIG: I did this no matter what and never touched this investment for a decade.

I also increased the monthly investment as soon as my career progressed so not to fall into the increased lifestyle trap like I observed my peers were doing.

This is admittedly a “boring” strategy than anybody can follow and does not require you to learn exotic options or get any insider information.

After I started a decade ago, also my mum, my little sister, my girlfriend, my old uncle and a few of my friends (all of them completely alien to any financial knowledge or investment experience) also took this (long-term) approach with excellent returns.