Except for the Arctic regions, and Siberia, much of today's "Mother Russia" was in Moslem hands just 250 years ago. All of Kazan was Moslem for example.
Actually Tatarstan is considered predominantly Muslim Republic within Russia, and they are allowed to fly their state flag higher than the Russian flag. As well, street signs in Kazan are in both Arabic and Cyrillic lettering ( I have been there...).
Kazan was sacked more than a dozen times in it's 1000 year history- including by Ghengis Khan and his golden horde. As to whether their population was ever so large - do not forget that they lost about 26 million during WWII, and Stalin was responsible for executing or starving to death some 8 to 10 million Ukrainian Kulaks, and another 15 to 25 million other enemies of the state besides.
The revolution between the Red and the Whites, Leninists and Trotskyites was more costly for them than the Civil War was for the US (which was more costly for us than was WWII).
Just a few thoughts
A.A.C.
The Final Crusade has commenced.