Bounties are placed with the hope that someone will attack and collect the bounty. However what if a person is so unfathomably strong that the marines know it'd be suicide to throw anything less than 4 Admirals at him...
Rather than have their entire marine force be wiped from losing to him, they could protect their soldiers. This is especially valid as he is not technically a pirate, it would also provide more than enough reasoning for them to beg him to work with them.
Rather than have their entire marine force be wiped from losing to him, they could protect their soldiers. This is especially valid as he is not technically a pirate, it would also provide more than enough reasoning for them to beg him to work with them.