We're also harboring the illusion that a former Muslim could rise to the top spot in the Soviet Union. The leader would have had to have been a former practitioner of Orthodoxy. Being a heretical Mohammedan was only one step above being a Jew. No, the leader had to be 100% Russian for the people to accept him. And before people mention how Stalin was Georgian, I'd like to point out that Stalin's own kids didn't even know he was Georgian for a quite some time. Svetlana learned it from her brother, who said that "Apparently father used to be Georgian." or something to that effect.
It would hurt his career to be muslim born, but kill it?
Are there specific books/events you base your theory on?
Of the soviet leaders Lenin was of mixed ethnicity, Chrustschow was an Ukrainian (I admit thats not very diffrent from Russian but still not 100%), Breschnjew was an Ukrainian that later changed his ethnicity to Russian.
And keep in mind that Stalin was not elected/choosen to be the big leader.
In the begining he was a bureaucrat that Lenin installed as General Secretary after he had his public fall out with Trotzki over the unions and grew weary / distrustful of the old aristocratic-theorist leadership.
Later the Sinojew clique and the rightist left him in that position of power (and allowed him to expand it) because they needed him to do their legwork in the fight against Trotzki.
He used his power to get croonies into the important positions and gradualy outlaw his former allies.
Only after he had total controll, he created a public cult around himself and presented himslef to the public as glorious leader. (before he was only the humble servant of the party)