many churches

Historically of course.

The Knyazh (Duke) Vladimir accepted Christianity in 988 to unite country. In 1237 the large part of Russia was invaded by Chinese tribes from the territory currently Mongolia and North Chine. This period is called as Mongol-Tatar Yoke.

But tribes from North Chine invaded Arabic countries as well.  This is why the close link was made between Arabic part of Great Empire and people from tribes had settled on the east and south part of Russia and native people too.

By the economic, trade and other ways Muslim religion had came to Russia. And a bit latter but by the same ways Buddhism had came to Far East Russia from India across  East Chine.

It is very shortly! But question is nice because in now days only few people think about the way the religion they have got.     Good luck!

Most of russians are very religious people