If you surround yourself with yes-men/women, you will eventually believe them. Most normal humans literally cannot afford to do that because you can't buy groceries with ego, but if you disconnect yourself from normal life by being one of the privileged few born with a silver spoon in their mouth and connections before leaving the womb, you can avoid reality for a long time.

If SBF was born to an average family, none of this would have happened and he might even be a normal person, maybe a little cocky. Or he would be constantly struggling to live a basic life between jobs as he keeps being fired or let go for being insufferable.

I highly doubt he would have gotten into Jane street