Caesar Clown started making Smiles on Punk Hazard after the Aokiji and Akainu fight. Which happened about 2 years ago. The only smile to have been made before that was Momonosuke’s.
But Kaido was an Emperor known as “King of the Beasts” way before this. Or at least before Water Seven when the first mention of Yonko happened.
None of the Headliners we’ve seen were on his crew back then or actually had Devil Fruits since it’s only Smile users (or Supernovas) so far.
Not to mention the entire concept of Gifters couldn’t have existed before Caesar as well. And to make it stranger, there’s the massive difference in strength between Headliners despite them being the same “rank” that people have been questioning.
My theory now is that “Headliner” isn’t really about strength. It’s about the time you entered the crew. My theory stems from Oda’s strange introduction of the only character who, we can be sure, isn’t a new member of the Beast pirates, Jack the Drought. His Oda box had actually one title, “Lead Performer”.
The term “Calamity” that’s very common is just a description of Jack and Kaido’s top men. The actual title is “Lead Performer” and this is in direct reference to Japanese theatre the same way “Headliner” is as well. These titles are given according to the order in which the artist appears on stage.
Therefore the Headliners, Gifters, and probably Pleasures are technically just Rookies in this Yonko crew.
Similar to our old friend Rockstar in Shank’s crew or Pinkbeard in Teach’s crew, the big difference between the Beasts Pirates and the rest of the Yonko crews is that Kaido gives rankings based on the time one joined the crew. Bege became a Rook because of working hard but in Kaido’s crew, X Drake is a Headliner along with Speed no matter what he does.
In conclusion, aside from Jack, we might not have actually seen any of the actual Beast Pirates(or at least their top fighters) that helped turn the Beast Pirates into a Yonko crew.
*Theory by ImmaIvanoM