The underlying theme behind the deconstruction of the Beast Pirates is the realignment of their forces allegiance. What initially began as a group of fighters that constituted two pirate crews, a few Samurai, a ninja and the Mink turned into hundreds than an army of thousands before the raid on Onigashima. Such a theme carried forward through the story of Onigashima with it still continuing. The disparity in numbers between the two forces continues to close with the Samurai Rebellion on the path to growing larger than the Beast Pirates force. It has been set-up to happen. And it will happen. The whole Onigashima story has been building up toward Luffy taking Yamato away from Kaido.
On the journey to Onigashima, the first major turn began with Kyoshiro revealing his identity (Denjiro) and allegiance to the Kozuki family. The Samurai Rebellion force was bolstered from 4,200 to 5,400. Further into the arc, X Drake’s undercover operation is burned and he abandons the Beast Pirates to throw his lot in with the Straw Hat Pirates + Samurai Rebellion as an army of one.
When the Ice Oni virus is released by Queen, Hyogoro exploited its affliction to turn its power back on the Beast Pirates as it temporarily returned him back to peak strength. Chopper used the antibody Queen made to base his own virus creation that nullifies the Ice Oni virus. The compassion and understanding Chopper showed melted the hearts and fear of the Ice Oni virus from the Pleasures and Waiters subject to Queen’s cruelty and heartlessness. As a result, the 4,000 Pleasures and Waiters present on the Performance Floor turned their back on Queen and the Beast Pirates and sided with Chopper and the Samurai Rebellion.
The development between Nami and Zeus continues from the Whole Cake Island Arc with Nami completely winning Zeus over here after being targeted for extermination by Big Mom. Tama is given the opportunity to use her Devil Fruit powers on Onigashima and as a result of issuing the order for those that consumed her Kibi Dango to shift sides to help Luffy and Momonosuke, about 300 SMILE users turned on the Beast Pirates. Subsequently, this is turn caused the followers of some of the Headliner’s to join the Samurai rebellion – roughly a thousand.
With the Beast Pirates forces dwindling, it is only a matter of time before the Oniwabanshu and the Mimawarigumi, which numbered 5,000 each before the start of the battle (10,000 in total), turn on the Beast Pirates. I suspect this is part of the reason for why Hiyori has been saved for this point in the arc. Hiyori’s appearance, message and resolution will catalyst another shift in allegiances. The realisation of the battle she has been fighting for 20 years will inspire those once loyal to the Kozuki clan to remember why they made such a commitment in the first place. Momonosuke’s reappearance and transformation will be saved for a different development. I wouldn’t even be surprised if the Numbers, Apoo and Hawkins eventually turn on the Beast Pirates. Usohachi, the sibling hunter, is already displaying his power to win over undecided Beast Pirate soldiers.
Even Kaido’s Mythical Dragon Devil Fruit powers are being used against him thanks to Momonosuke and Vegapunk’s Artificial Devil Fruit. Everything that makes the Beast Pirates such a terrifying force is being deconstructed and consumed by the Samurai Rebellion.
At present, Kaido does not believe there is place within the hearts of the Wano people or humans in general for acceptance of Yamato. Due to his own past, such a context has become his truth. Once Kaido is made aware of the current state of the Beast Pirates and arrives at the realisation his plans are beginning to crumble in front of him, Luffy will deal the final blow and express his intention to also “take” his son, Yamato, away from [New] Onigashima i.e. aboard his ship. Bathed in such a reality, Kaido will come to know defeat and the narrow-mindedness of his perspective.
The Straw Hat Pirates are also meant to be a reflection of the Rocks Pirates in regards to their strength but a deviation in terms on their bonds and relations. Fear, power and ambition kept the Rocks Pirates together but when they met a wall they couldn’t pass, they collapsed. The Straw Hat Pirates have since entering Wano encountered numerous walls and have yet to crumble as Kaido suspected, expected and believed only possible. The bond Luffy has with Yamato will be the revelation that shatters Kaido’s perspective on the world, pirates and possibilities.