I thought the same thing and thought I'd misread the article.
This is what I remember of Russian-Chechen relations:
The deadliest school attack in Russia took place in 2004 in the city of Beslan, when Islamic militants took more than 1,000 people hostage for several days. The siege ended in gunfire and explosions, leaving 334 dead, more than half of them children....Perpetrated by militants linked to the separatist insurgency in the nearby republic of Chechnya.
I think people overestimate ethnic and religious loyalty. During the crusades, the Crusader states and the Muslim states would sometimes team up to take on Muslim powers in the region that were a mutual threat. Another example is France and the Ottoman empire’s alliance against Austria-Hungary in the 1600s.
Power is more concerned with sustaining itself than loyalty to country or ideology.