The pilots of the accident flight reported bird strike and difficulties handling the plane's flight control systems.
From FlightRadar24, the pilots struggled with flying the E190 for more than an hour during the diversion and attempted emergency landing at Aktau, Kazakhstan before crashing.
The pilots could've choose to land at their intended destination at Grozny, Russia (and it was closer than Aktau), but the weather conditions at their destination airport is reported to be foggy enough that the pilots chose to fly across the Caspian Sea for an attempted emergency landing at Aktau.
Seems like the bird strike (if the reports are true) did some serious damages to the E190's flight control systems (flaps, hydraulics, ailerons, etc). The pilots fought real hard to the very end, as evident by the repeated pull-up attempts by the pilots prior to the crash in the video below.
One thankful instance was that the plane crashed in a shallow dive instead of a nose dive, hence many of the passengers seated in the rear section survived as the tail section broke off upon impact and wasn't damaged by the subsequent explosion and fire.
May the survivors recover from the crash, and may the deceased rest in peace.