By what "external power"? There's some evidence that Germans aided and financed the initial stages of Russian revolution, but its pretty weak, and its effect is unlikely to have been decisive. The revolution was largely a consequence of the war, weaker government, pissed off populace, and the fact that people didn't really know what they _really_ were signing up for. Now that several regimes have gone through the proces, we do very much know where these things end. Except for maybe the folks in their teens and mid-20s who don't study history and therefore might be doomed to eventually repeat it.