well WWI would probably still happen, as other powers like Germany or Austria Hungary would probably invade Russia, and then Russia would invoke its military alliance and then all of Europe would go up in war like as in OTL, only with it starting in Russia in stead of Serbia. Russia would probably be weakened by the explosion anyway, so they would do badly as per OTL except that nationalism from being the victim of an aggressor would make the people fight harder methinks. However I think that in the end the autocracy would fall anyways due to it being horribly ass backwards. I was actually thinking this event over recently myself and was looking into a TL involving Russia arising from WWI as a Theocratic fundamentalist state due to the population viewing the disaster as divine retribution on the hedonistic and corrupt Czar and his family.