"I would like to say that little Serbia was not the reason for WWI, but rather Austro-Hungarian imperialism and bullying." Right idea, wrong country. It was Germany's imperialism and bullying which pushed the Austrians into declaring war on Serbia.
In fact, Austrians didn't much care about the loss of their Archduke. They didn't like him or his wife, and were just as happy to see them dead.
It was German leaders who needed an excuse to do what they had planned for years. Pushing Austria to invade Serbia gave Germany an excuse to invade France and Russia.
Please, I beg, for anyone who thinks you understand what started World War One, please read the following book:
Europe's Last Summer
I did not write the sentence you referenced. I am a history buff and have read extensively on WWI. If you want to look at outlying causes to WWI you could go back to chancellor Bismark. After the Franco/Prussian war of 1871, he knew that France was itching for revenge. So he wanted to isolate France by making alliances with central European powers such as Austria Hungary and Italy. In response, France, UK and Russia made an alliance to counteract. It was these alliances that triggered the dominoes falling that led to WWI.
The fact of the matter is that the actual cause of WWI was Gavallilo Princip murdering Archduke Ferdinand and his wife that led to WWI. If this did not happen, there would be no WWI in August of 1914. Whether Ferdinand was disliked by King Josef or not has no bearing. No kingdom is going to sit back and allow the heir to their throne (especially when Josef was in his 80s) be murdered.
It’s true that Austria Hungary did have Germany’s backing to push their little war, but it was Austria Hungary’s unrealistic demands on Serbia (essentially making it a vassal state) that tipped the scales of war. In fact when Austria Hungary declared war on Serbia Kaiser Wilhelm was actually on vacation.
It’s funny, because the houses of Hohenzollerin, Hapsburgh, Romanov and Windsor are all interrelated and yet they all went to war with one another and three of those royal houses were destroyed because of it. The causes of WWI are many and varied, but the match that set the fire burning was undoubtedly the assanation of the heir to the house of Hapsburgh in Sarajevo.