Why did a local conflict between austria-hugary and serbia result in a global war?

In short, the conflict stemmed merely from Austria-Hungary and Serbia’s disagreement over how to handle the assassination of Archduke Ferdinand: the Austro-Hungarian government believed that the Serbian government was connected with the assassination and therefore demanded to be involved in the investigation and judicial process within Serbia.

Explanation:

the group i'm selecting: greeks.

a first group of greek immigrants came to the us in the 1850s. the second group came to america starting in the 1890s due to economic opportunities they didn't have back in their home caused by the hardships of ottoman rule. greek immigration was 90% male, many of them expected to work and return to greece after earning enough capital, but ultimately had to remain in the us after the greek genocide.

i believe it is capitalists.