Those levels of total comp are mostly in stock. Stock compensation has a non-trivial level of luck in it. Join the company at just the right moment (knowable only in hindsight) when the stock is lower and then keep vesting as the stock skyrockets.

BTDT but I don't pretend it's my magnificent skills (although I'm good), it's just the luck of the draw with stock compensation. I'm just as good in other jobs where the stock performance has been lackluster.