Maybe they were thinking that they can chest and handle the attack since they are Russian
“How Russia ‘Ignored’ U.S. Warning Of ISIS Attack That Killed 133, Injured Over 140 In Moscow - SaharaReporters.com”
“How Russia ‘Ignored’ U.S. Warning Of ISIS Attack That Killed 133, Injured Over 140 In Moscow - SaharaReporters.com”