To calculate the % of luck needed to win the WSOP main event, is almost impossible. Think about it, 5K+ players, Top professionals, internet qualifiers, donks etc. To get anywhere near the final table you need to win a lot of all in's. You have to win all the ones which your ahead in the hand pf, and you will have to win a fair few were you will be behind, even with one card to come.
So with huge fields like this you will have to be really lucky to get the final table, never mind winning the thing. If you look at the other events at the WSOP, with much smaller fields and more specialist events, you see the top names making the final table time and time again. The luck factor in this instance has been reduced somewhat, because the cream is rising to the top so to speak, due to reduced fields and inexperience in the event. The main event is almost a lottery.