Unrest in Austria-Hungary and the rights of Serbia were just excuses.
It was all about the Turkish Straits - for rather strong geopolitical and economical reasons, I'm not saying that the Russian leaders wouldn't have had good and perfectly understandable reasons to act like they did.
But that doesn't change the fact that after the Treaty of Berlin Russians had been happy to keep Balkans on ice in full accord with Vienna while they focused on Manchuria. After the defeat against Japan Russia and Austria-Hungary continued their traditional cooperation until overly ambitious Izvolsky burned his fingers at the Bosnian Annexation Crisis, and the relations with Austria-Hungary were ruined for good.
Subsequently Russian diplomats acting more or less according to their own wishes orchestrated the creation of the Balkan Alliance, lost control of it, and alienated Bulgaria in the following wars that destabilized the region even further. By 1914 Russians were anticipating a complete breakdown of the moribund Ottoman Empire, and at the same time felt that their "national prestige" could not stand another humiliation at the Balkans. Hence the OTL politics. The Russian leaders were not hell-bent on setting Europe aflame, they merely pursued politics that they deemed vital to the strategist interest of the Russian Empire, but at the end of the day their actions played a large part in making the disaster that was WW1 happen anyhow.
It was all about the Turkish Straits - for rather strong geopolitical and economical reasons, I'm not saying that the Russian leaders wouldn't have had good and perfectly understandable reasons to act like they did.
But that doesn't change the fact that after the Treaty of Berlin Russians had been happy to keep Balkans on ice in full accord with Vienna while they focused on Manchuria. After the defeat against Japan Russia and Austria-Hungary continued their traditional cooperation until overly ambitious Izvolsky burned his fingers at the Bosnian Annexation Crisis, and the relations with Austria-Hungary were ruined for good.
Subsequently Russian diplomats acting more or less according to their own wishes orchestrated the creation of the Balkan Alliance, lost control of it, and alienated Bulgaria in the following wars that destabilized the region even further. By 1914 Russians were anticipating a complete breakdown of the moribund Ottoman Empire, and at the same time felt that their "national prestige" could not stand another humiliation at the Balkans. Hence the OTL politics. The Russian leaders were not hell-bent on setting Europe aflame, they merely pursued politics that they deemed vital to the strategist interest of the Russian Empire, but at the end of the day their actions played a large part in making the disaster that was WW1 happen anyhow.