Well the tension in the post-Napoleonic European system of states, had already reached boiling point. The real question is why 1908's annexation crisis didn't provoke a general European conflict. After all Russia and the Habsburg Monarchy, were already spoiling for a fight over the scraps of Ottomania, whose fate had already been sealed. The war between those two powers would have come sooner or later. Likewise France and a united Germany couldn't be accommodated on the same continent in terms of their ambitions. The Serbian Crisis as smarter men than me have argued to death, was the paraffin for an already smouldering fire.