Why is Arlong weak, Oda hyped Arlong by having him be capable of ruling East Blue with the help of Nami maps.
Arlong
believed he could have ruled East Blue. The reality is he was hopelessly deluded and if it wasn't for corrupt Marines he'd have been crushed by someone, probably Smoker.
He was strong at the time, but he was a literal big fish in a small pond. It's also hard to compare a character Oda hyped in the first 100 chapters of the series, when the characters were the weakest they've been, when we barely knew anything of the world, to ones we are seeing now, where (wild cards like Imu, Rocks and SSG aside) we have a pretty good idea what the balance of power really meant. If you take Rocks and SSG, for example, who have been introduced in the ~150 odd chapters since Germa, you see a real difference in how they are hyped. Again, Rocks and SSG get known quantities. Something strong enough to replace the Warlords. Roger's greatest foe, who fought him and Garp and had three of the future Yonko on his crew. Germa had nothing compared to that.