Your premise is wrong in a couple of ways. First of all, the Russian Revolution did not happen because of WW1. It certainly didn't help (or did help, depending on whose perspective you take), but it was a long time coming. Only a few years earlier there had been the Revolution of 1905, which achieved little on paper and even less in reality. Most of what it did achieve was quickly rolled back. Now, that revolution took place in the context of the Russo-Japanese war of 1904-05, but there were strong underlying issues even so.

We like to look at the Soviet system of government as an authoritarian contrast to Western democracy, which is not a helpful perspective in this context. Instead, compare it to the governance of Tsarist Russia, which came before it. It was a fundamentally undemocratic society, with poverty, illiteracy and state brutality. Stalin did not come up with the idea of sending prisoners to Siberia, to put it that way. As such, World War 1 only magnified the issues that were already present.

Secondly, even if we were to accept that WW1 caused the Russian Revolution, it does not follow logically that WW2 would cause another revolution. While citizens of the Russian Empire certainly grew tired of the war quickly, they lay the blame on their rulers. This is different from WW2. You could almost argue that Hitler did Stalin a big favour by not only invading the Soviet Union, but breaking a formal agreement in the process. The hardship in the face of the German invasion created a genuine sense of patriotism and collective sacrifice which was masterfully exploited by propaganda.

Stalin was in a much stronger position after the war than he had been before it, even among groups he had persecuted. It had allowed him to create an incredibly strong sense of explicitly Soviet patriotism, which had not really existed before. No revolution was ever likely to come out of that.

Since Nimonic more or less answered the main question, I would clarify this bit.

30 million killed by Stalin's wrath.

I must say, the actual numbers of the people "killed by Stalin" should be 1,000 (one thousand) times less. The most coherent accusation are the so-called "Stalin's shooting lists" - people that Politburo (the whole committee, not Stalin alone) allowed NKVD to investigate under the "special provisions" act (the one that got introduced in 1934, after Kirov's murder). That was ~44.5 thousand people (as per "Memorial" claims) in toto in 1934-1953, but only 39 thousand of them were accused of execution-worthy crimes, not all of those 39 thousand were found guilty, nor did the Stalin personally participate in signing some of the lists.

 

And - yes. Obviously, all that presupposes every suspect being innocent and wrongly convicted.

 

P.s. Yes. I'm aware of Black Book of Communism, but I don't find it's arguments persuasive. Arch Getty's books (despite his deeply anti-Soviet position) are much more coherent, especially when it comes to sources (a huge problem for most books on USSR), unlike Getty's personal opinions about USSR or Russia in general (his idea of some special Russian "patrimonialism" is ludicrous, to say the least; especially in light of Soviet preponderance of collective decision-making).