Yishan Wong (ex Reddit CEO, and thus someone who would be in a position to know) said Ohanian did it as part of an attempt to change how Reddit handled AMAs, an

Yishan Wong (ex Reddit CEO, and thus someone who would be in a position to know) said Ohanian did it as part of an attempt to change how Reddit handled AMAs, and criticized Ohanian harshly for his actions and failure to defend Pao. Ohanian, for his part, has never denied it, and in fact has apologised for the "decision to change how we work with AMAs" as "his failure". I personally consider that confirmation.