Why is the World NOT led by Muslims

Why is the World not led by Muslims?

 

A profound explanation of the following comment/ question using Surah Al-Fatihah: -

"In the past when Muslims were very few (in numbers), and resources were limited, but as an Ummah we were leading the world. Today, by numbers we are many and by resources Allah (swt) has blessed us with many resources, but look at the Muslim Ummah's status in the world, we are nowhere close to the way the Ummah was in the past."

 

Why is current situation as an Ummah like that?