What caused the fall of the Ottoman Empire?

Answer 1

Ottoman power began to decline in the late 16th century. Ottoman forces repeatedly besieged Vienna.

After their final effort at taking the Austrian capital failed (1683), that and subsequent losses led them to relinquish Hungary in 1699. Corruption and decadence gradually undermined the government.

In the late 17th and 18th centuries the Russo-Turkish Wars and wars with Austria and Poland further weakened the empire, which in the 19th century came to be called the "sick man of Europe." Most of its remaining European territory was lost in the Balkan Wars (1912 – 13).

It sided with Germany in World War I (1914 – 18); postwar treaties dissolved the empire, and in 1922 the sultanate was abolished by Mustafa Kemal Atatürk, who proclaimed the Republic of Turkey the following year.

Answer 2

Spread too thin. Poor administration. Bad politics. Cruelty. Boneheadedness. Corruption.