I don't know if this has been mentioned before or not but…
Is it just me or do the Shichibukai work for the WG, perhaps Crocodile made BW under orders from the WG, and the WG just tried to cover it up by sending in Marinese and arresting the members.
Like right now CP9 is a very secretive group that not many people know about. BW could have been controlled completely by the WG through Crocodile, just making it look like a criminal orginization.