The confirmation that Zoan devil fruits have a mind of their own was even bigger news than the true nature of Luffy’s devil fruit.
So far the only objects imbedded with devil fruits were Zoan fruits. Never Paramecia or even Logia fruits.
And that makes complete sense now. A person eating a Zoan might be subtly influenced by it, like becoming more aggressive in case of a predator for example but largely remain the same person.
If an object however is infused with a Zoan fruit, there is no personality to hold the fruit’s inhibitions and will in check. That’s why these items seem to have a mind and personality of their own. It’s part of the fruit’s ability.
Maybe this is also the secret to Vegapunk deeming Momonosuke’s dragon fruit a failure. Maybe he was able to replicate the fruit’s abilities, but could not inherit the will of the original into the copy.
Moreover, this synergizes with the fact that SMILEs were failed Zoans that led to people having an obsessive fake-laughing trait.
So Kaido asked Caesar to create artificial devil fruits just like Vegapunk.
Kaido knew what involves Joy Boy and who he was 900 years ago, so he told Caesar that his devil fruits had to come with a will, with a joy, with an immeasurable smile and laugh.
Caesar added this factor to his fruits, that’s why they are called SMILEs.
When one receives an artificial devil fruit and makes the bond, they get Zoan-like abilities but not the will or joy of Joy Boy/Nika.
When an artificial devil fruit doesn’t work, the side effect of it is the eternal laughter. When the SMILEs recipients can’t handle the nature of the Nika devil fruit they get overwhelmed by it and become unable to show sorrow.
SMILEs are called SMILEs not because of their side effect when they don’t work, but by their primary intention which is to have JOY in them.
Maybe Kaido was trying to infuse the “laugh” nature or the personality of the last Joy Boy’s devil fruit with the dragon fruit in order to become the new Joy Boy.
*Theory by shipposterkatakuri/Environment-Left