Look at the papers from the time, pretty much everyone was excited to finally stick it to the germans. Belgium did draw a bad deal from it. Maybe germans pushed Austria against Serbia.. however assassinating Archduke AND his wife might have had something to do with it too you know..
Lenin took power way after the first revolution (that forced Czar out). Kerinsky and the rest continued the war which empire was losing by that point in a spectacular fashion. As much as people want to believe in opposite Russian empire was in bad shape when war started. Then completely incompetent command of the army etc did the rest. Russian loss to Japan 10 years earlier was the first sign of the end.
Of course common people of all countries were "enthusiastic," because they were naturally patriotic. Their "enthusiasm" lasted until the first major bloodshed stripped away everything but fear and determination.
Can anyone seriously argue that the average French soldier was more or less "enthusiastic" than typical German or Austrian soldiers? I don't think so. So common "enthusiasm" was meaningless.
What matters is, which country's leadership wanted war and started war? Yes, of course, no average citizen in 1914 believed their country started the war. But looking back carefully through all the documentation, it's most clear that one country's leadership did want war and did start it. That country was Germany.
If you wish to debate how, why and when it all happened, I'm happy to do that. But again, I'll recommend David Fromkin's book: "Europe's Last Summer".
And while you're at it, read Barbara Tuchman's: "Guns of August". It is excellent, but devotes only ONE SUMMARY PAGE, just before chapter 6, to all those events which Fromkin's book covers in great detail.
The two books together will give you a pretty good understanding of what happened, and why.
Here's the bottom line, according to Fromkin: the war's outbreak was driven by the German General Staff, specifically its chief, General Helmuth von Moltke (the Younger), whose chief aid in charge of war plans had been an unknown colonel named Eric Ludendorf.
Of course the Russian Empire was in bad shape -- that's not even debatable. But when the Tsar was overthrown, it was by real democrats (small "d") highly friendly with and probably even supported by the Brits. These people were determined to keep Russia in the war, however badly it went -- for reasons of obvious benefit to the Brits and French in the West.
Lenin's crowd was the "peace party" sent & paid by the German General Staff (read: Ludendorf), specifically to take Russia out of the war, and so free up hundreds of thousands of German troops (50 divisions) to fight in France.
And it ALMOST worked -- if not for the good showing of a plucky band of new allies in June 1918, then fighting their most critical battle at a place called Belleau Wood.