When the Mane Mane no mi user instructs Orochi to gather gold and create weapons, it proves that
he/she is a member of CP0.
Wano was once a country where gold was heavily sought after by pirates, so it would make sense that the WG has always wanted to get its hands on it as well.
The weapons speak for themselves, Orochi began the international trade of weapons with the Underworld/WG which would eventually lead to Kaido’s trade deal with Doflamingo and the SMILE.