May revealed surviving members of Queen feared the comedian's presence would distract fans from the flamboyant frontman's life story, reported Contactmusic.
The "Ali G" star walked away from the project in July after spending months perfecting his vocals for the role, amid rumours he had fallen out with May and Roger Taylor over his planned portrayal of their late friend and bandmate.
Cohen has yet to comment on his reasons for quitting the film, but May has now shed some light on the actor's departure, insisting he just wasn't right for the job.
"And we thought there has to be no distraction in the Freddie movie. You have to really suspend that disbelief - the man who plays Freddie, you have to really believe is Freddie. And we didn't think that could really happen with Sacha," he added.
However, the guitar icon is adamant that claims of a bitter rift between the Queen stars and Cohen are completely unfounded.