So to wrap it up - the Russian revolution basically proved the essence of Marx' ideas to be right, in that it really was the Russian proletariat that carried the revolution.

I don't think this is really so. In the first place, the architects of the Bolshevik Revolution were lower-middle-class educated people like Lenin himself -- what Eric Hobsbawm later called "the lesser exam-passing classes" -- not horny-handed sons of toil, on the assembly-line or anywhere else. In the second, this was not so much a "revolution" as a coup, carried out by an almost insignificantly tiny minority of the Russian population. Perhaps the German term Putsch might be even more appropriate. In ordinary circumstances, it would have gone no further than Hitler's similar attempt at the Burgerbraukeller in 1923. But in the chaos of the First World War, with the front collapsing and the armies voting with their feet, these were not ordinary circumstances, and there was no functioning state apparatus in St Petersburg to do what the Bavarian police did efficiently and imperturbably in Munich on the latter occasion: haul the "revolutionaries" off by the collar to jail and have the courts give them a good spanking until they promised to behave themselves.

It took a fantastically unlikely set of circumstances for the Bolshevik groupuscule of October 1917 to be able to scale this fairly insignificant event up into the exercise of real power. One of the most important, though neglected, components was the defeat of the German Empire a year later. If the Central Powers had won the war, and the Treaty of Brest-Litovsk had stood, Lenin's regime would in all likelihood have lasted no longer than Kerensky's. This was one of the many things in which everything that could possibly have gone right for the infant Soviet Union did.

The real "revolutions" came later, in the form of a series of increasingly brutal campaigns from above by the regime against its own people. Those were always required to sustain the system in being, and the moment the taps of repression were turned off in the late 1980s and early 1990s, it instantly collapsed.

To revert to OP's question, the reason that proletarian revolutions didn't happen in "wealthy, industrialised and urban states" is that basically from the moment of the Communist Manifesto's publication, the working classes in those countries embarked on a steadily, if unevenly, upward trajectory in terms of living standards and access to political power. The prediction that their increasing immiseration was inevitable had already been disproven by the end of the nineteenth century, as the German socialist Eduard Bernstein pointed out in great detail in his devastating critique Evolutionary Socialism in 1899. And by the 1950s, cultural Marxists like Herbert Marcuse had so written off the proletariat as a source of revolutionary fervor that the only people in Western societies on whom he was pinning his hope were people outside the economic system altogether like incarcerated prisoners and university students.

One of the answers involves the previous state's degradation and loss of their monopoly on violence. Communist revolution was a real threat to many established states and occurred in Germany, but subsequently failed in its infancy. Whereas in Russia, the Communist revolution gained steam, and supplanted not only the Czar, provisional government, and the whites, but also eventually the peasant revolution. Comparing the two might give a better idea on how the revolutions were able to take and hold onto power, or not.

First, Germany had an attempted Communist revolution with Karl Liebknecht and Rosa Luxemburg leading it in Berlin. The revolution was encouraged and egged on by the revolutionaries in Russia, despite the inability of them to support it. Lenin was hoping for a spontaneous world wide workers' revolution, and he along with many others, thought that the revolution would grow as the Communists in Germany simply rose up. These attempted revolutions happened in the same time frame with different outcomes. The German military brutally put down the revolt, and maintained a monopoly on violence.

The nation states around Germany did not want a communist revolution there. They sent aid and support to the newly organized militia groups known as Friecorps and turned the other way when the disarmament rules were bent to put down the revolution. The Friecorps consisted of battle hardened WWI veterans that were highly nationalistic. They had a signed peace deal and turned the revolution's timing against itself for support.

The German military used the revolution's timing to raise support for nationalism. The "stab in the back myth" precipitated, stating that revolutionaries at home were to blame for Germany's defeat in WWI (and also a vast Jewish conspiracy). The propaganda was an effective tool to maintain support, especially among nationalists within the military. The peace treaty was signed, so the prospect of a long war was not able to be used by Communist factions. The Friecorps organized quickly and effectively to put down the various revolts, being all united in one front with one purpose, instead of many competing groups. All of this is in stark contrast to Russia.

Russia's military was losing the war, and it was pinned on the ruling powers. Czar Nicholas II took direct control of the military against the advice of nearly everyone. He thought that if he was at the head of his military, they would fight harder. In actuality he mismanaged the military even more than the previous commanders AND put himself in the blame seat for losing the war. The Czar's administration also woefully mismanaged the distribution of food and the production of goods. Furthermore, the military was busy losing a war while not being at home to maintain the monopoly on violence, whereas the German military just returned from the fronts. Disgruntled peasants started to seize land, only aided by deserting soldiers that returned home with their guns in hand.

The provisional government was set up, with the Czar abdicating, but all of that was too little too late. The Czar was slow to give up any real power to a democratic government, only doing so at the last minute. The country collapsed into what really can be described as anarchy. Due to Communist propaganda, the military started to join the Reds and/or return home, whereas the officer class joined different competing armies. The provisional government cold not maintain troops in order to protect itself, as it did not have effective support from the old leadership. That was in contrast to the Reds whom simply took soldiers to Moscow and deposed that government. A single Latvian Rifle division joined the Reds and stood between the Reds and collapse at this time, but that was much more than anything the current government had. The Reds maintained Moscow and gained support for itself as it negotiated peace. It then started to fight a civil war against different armies.

The whites lacked any unity of organization, with the only purpose of restoring the old order. They were spread out along the periphery of the empire, and opposed not only the Reds, but also the peasant revolution. Many mini nameless wars were fought over peasants and landlords, lords which the whites supported. The whites had almost no production and hardly any support outside of the old officer class. The Reds gained control over the core of Russia, and the whites were slowly whittled away, partly buttressed by a Czechoslovakian division that Trotsky unwittingly spurred into supporting the Whites. Overseas support could not really reach them, and even the small Allied army did little up around Finland. The Reds gained a monopoly on violence more because there was a lack of any real contender, or any kind of wide support for a contender.

Germany's state had a dedicated national military, it spun the revolution as having lost the war, it was more concentrated in a smaller landmass, its military had a single organization, it had direct material support from nations with surplus military equipment, but ultimately people did not abandon it. Compare that with Russia's state, the Czar was blamed for the war, the military was deserting in droves, the provisional government lacked support, the whites were divided, the whites fought against two different revolutions, the Reds positioned themselves as the solution to WWI, and overseas support for the whites was almost impossible. One revolution happened in a state with a somewhat firm monopoly on violence. The second happened in a state that had decayed into anarchy.

Stephen Kotkin, a professor of Geopolitics, writes in his biography of Stalin about how, if not for the one Latvian rifle division, the Reds might have collapsed in their push on Moscow and the holding of it. He continues to say how a small German force almost collapsed the Bolsheviks, forcing them to sign a quick peace in WWI. He contends that it was not really huge support for the Reds that won (citing low party membership numbers even in their own military, among other data), but the fact that everyone else had lost almost all support. A similar environment seems to have happened in China as in Russia, however with a much longer civil war. One difference being that the Chinese Nationalists had effective support but then also had to fight Japan, leading to exhaustion.

I do not know if that helps anything, but it a more realist and geopolitical take on the Communist revolutions in Russia and Germany.