Aljamain Sterling pulled out of his first title defense and rematch against Petr Yan due to issues with his neck, and the UFC decided to book an interim championship involving Cory Sandhagen. Rob Font was apparently another name that was in consideration, which does make sense from a rankings perspective.
Yan is ranked number one at bantamweight. Number two is T.J. Dillashaw, who is still injured, and the third ranked Cory Sandhagen is technically coming off a (somewhat disputed) decision loss to Dillashaw. Font is currently ranked at number four, but he revealed that he had to turn the title opportunity down.