Celestial Dragons are referred to as gods. The clan of D are mentioned by Corazon to be God’s natural enemy. We see Im Sama for the first time in the chamber holding Luffy’s wanted poster and then when we see him/ her again, he/ she has stabbed Luffy and Blackbeard’s bounty poster. So it seems like Im Sama hates the D clan and sees them as enemies and that has to go back to like the void century. Im Sama is probably the reason why Celestial Dragons are above everyone else in the world Government. He is probably the king of the Celestial Dragons because even the 5 Gorosie who are said to be the most supreme authority of the world bow before Im.