What if Blackbeard is mimicking Rocks’ recruitment strategy as well?
Blackbeard seems to gain his crews loyalty by offering them a powerful devil fruit. I think it’s possible that Rocks did the same, only he didn’t have any need to go hunting all over the Grandline for the most powerful fruits, as Blackbeard is having to. Maybe all the most powerful devil fruits were being hoarded by the Celestial Dragons, because they had control of the source, the sacred tree in God’s Valley. And Rocks promised his crew to track this island down, plunder it, and take the powers for themselves.
Maybe that’s why nearly every single member of Rocks Pirates (that has been revealed to us anyway) has such an incredibly overpowered Devil Fruit, while the other crew we’ve seen from the era, Roger Pirates, seemingly had no confirmed Devil Fruit users at all (save Buggy later down the line). Because, with a couple exceptions, the majority of the powerful Devil Fruits were in the Celestial Dragons’ control at that time, on this hidden island. Perhaps this power over the Devil Fruits distribution is what allowed the World Government to maintain their strangle-hold over the rest of the world.
THE GOD VALLEY INCIDENT
So how did the God Valley Incident potentially go down? Well, Rocks’ goal was to become the King of the World, and he wanted the power to take control, ie the power that the Celestial Dragons had, control over the Devil Fruit Tree. And perhaps he had a particular devil fruit in mind for himself…the dark dark fruit?
But Rocks would cause anarchy and bloodshed with that power in his command, the World Government is the lesser of two evils, so Roger and Garp work together to stop him.
They successfully stop Rocks from taking over the world. The status quo is maintained, and the Celestial Dragons are still in charge. Rocks doesn’t get his hands on the dark dark fruit, and he is lost to history. Maybe dead, maybe horribly injured, maybe imprisoned, we don’t know for sure. But he’s certainly out of the picture, and his subordinates are no longer loyal to him.
But the fight wasn’t a totally landslide. In the chaos, Big Mom was able to get Kaido his devil fruit. Whitebeard could have gotten his quake devil fruit, Shiki his float devil fruit, etc. And in the current age, you’ll notice that devil fruits are certainly more widespread. The Government no longer hoards these fruits for themselves.