Russians had two wars in Chechnya against Islamist insurgency. First War in 1994-1996 ended with factual Russian defeat (withdrawal). Second is 1999-2009 ended with Russian victory by installing pro-Moscow puppet.
Actually april 16 this year was exactly 4 years since Chechen defeat in second war.
Chechens were financed by that same Saudi groups. Russians are pretty well in control right now and it is hard to wage jihad at home so it is possible if they could hit US to prove Saudis they are still worthy to get their money.