F
I meant was it that he defeated the previous WSS or was he so triumphant that the title was made and recognized by the world to him.
I see a few possibilities but the most let's say "close to the truth" ones are:
Mihawk was constantly beating world-renowned swordsmen until the World decided to call him WSS.
He beat previous WSS/He retired and Mihawk was prominent with his name popping out everywhere you could find a strong swordsman engaging in a fight with the other one so people automatically jumped from fanboying previous WSS to Mihawk.
Mihawk and Shanks duels. This is the case I don't want the most because of one thing. If that's the case then it would mean that the winner of their duel was meant to become WSS yet Shanks lost his arm so people bestowed the title to Mihawk. I really really hope this one is not possible at even 1%.