El Hermano
Acclaimed
I think it can be explained by Buggy being a greedy bastard who'd rather pretend to be powerful and "manipulate" people into following and doing the dirty work for him rather than actually work his ass off to become powerful.Well originally Oda didn't plan the OP manga to go past the 5 years.
He also didn't plan the Novas or Shichibukai. He had the Yonkous and Admirals. Iirc he said in the interview the Shichibukai were one of the reasons the series lasted so long.