Did admirals know more about the void century?than we think? Think about it all the franky family didnt got any bounty in their heads, but franky did one why his the only one who got it? Its because even though franky burned down the ancient weapon text theres a chance that he read this text and already know about it. I think aokiji knew that theres definetely abchance that franky knew how to make the ancient weapon. Aokiji decided to trust luffy he knew that franky would joined up to them aokiji entrusted franky to luffy why so? Its because its dangerous for franky to stay in the water 7 who was once the one who keeps the ancient weapon. Aokiji leaving the navy i think he realize that he doesnt need to be one because theres so many ways to help people. Aokiji probably knew in 20 years there would be a certain pirates who will change the world and franky was gonna be part of this.