The admirals are the strongst fighting force of the NAVY, not of the WORLD GOVERNMENT. Get your facts straight.
The marines (NAVY) is the public face of the WORLD GOVERNMENT.
We were recently introduced with the GOROSEI and IMU that seem to be the STRONGEST FORCE of the WORLD GOVERNMENT.
So, very likely, the admirals are not the strongest force of the WORLD GOVERNMENT. They are the strongest MARINES but in the WG, there are even more powerful fighters: the Gorosei and Imu.
On the other hand, the YONKO are the STRONGEST PIRATES.
It’s not simply a fan thing, it’s a “fans with poor reading comprehension” thing…and in a manga for youths no less.