They only wanted to topple (and kill) the Tsar after unprecedented disasters in Western Russia (esp. After Poland and Riga). Without the supply routes cut and more troops available in the West, Tannenburg might be a stalemate, and Brusilov's offensive might be more of a success than OTL. Brusilov, with more success, might get his plans to the top command, thereby ensuring that the Russian Army will not get shredded to pieces like OTL. Yes, Tsar Nicholas was seen as an incompetent leader (militarily, economically a lot has changed since the 1880s) so I am really expecting him to abdicate, but the Monarchy will not be overthrown. Like I've said Alexei's too young, so a regent takes power. It might be Grand Duke Michael. There had been railroad construction in the years before the war, so transportation will not be such a mess. Thinking it would be like johnboy's "The Consequences of An Errant Shell" with a Japanese Victory in the Russo-Japanese War.