Question: why is usopp a god?
Answer: During the events in Dressrosa, Usopp awakened his Kenbunshoku Haki, making him the fourth member of the Straw Hat crew to demonstrate and use a form of Haki. 200,000,000, is a huge jump from his original, due to his role as "God" for saving all the toy slaves in Doflamingo's underground trades.