^ So I looked into it, and at the very least this aspect likely isn't taken from The Usual Suspects as Chapter 488 - where Bucciarati tells Giorno about the Boss and how nobody in the gang knows his face or name came out two months before The Usual Suspects aired in Japanese theatres.
Now I'm not saying the entire theory is bunk as Araki clearly made some changes to Diavolo between his first appearance when Bucciarati takes Trish to him and then when we see him revealed at last, and it's possible Araki incorporated some aspects of Soze into Diavolo later.