Russia would not have fought a war in Chechnya if it was not a part of Russia, in fact, 2 wars.
Kadyrov, the leader of Chechnya is the son of one of the main rebel leaders against Moscow, back in the day. A deal was struck.
ISIS has all Russian speaking brigades, an ISIS camp was found with Korans all in the Russian language. Uzbekistan, Kazakhstan, etc. they all speak Russian.