After the Great Fourth Shinobi World War, all the Kages are heavily injured, especially the 4th Raikage who lost his hand (which was answered nicely by Ankit Sharma here).
Now, the 5th Raikage selected was Darui, a shinobi of Kumogakure and the right-hand-man of the 4th Raikage. He may be capable of this position & may have proved his worth in the War.
On the other hand, here is what I think of Killer Bee:
- He is also a good & talented Shinobi.
- He is the brother of the 4th Raikage.
- He is a jinchuriki.
- He has a well-controlled of his tailed beast. He even taught it to Naruto.
- Even Minato, the 4th Hokage also praised Killer Bee on a fight with the 4th Raikage.
- He's the master/sensei of Omoi, Samui, and Darui.
- Having a good relationship with all other Kages.
- Unique fight style which I absorbed.
Considering this, why wasn't Killer Bee recognized as the 5th Raikage?