Question

why did mughals emphasise their  timurid not mongol descent?

Answer 1

When mongols were in decline and there was no strong leadership, then the Turkish and other Muslim's sought the chance and married mongol princesses and it was after this that the Timur's came in power. The Mongol's were not Islamist but then they started converting into Sunni Islam under the Timurid that's why I think the mughals emphasized the Timurid's.!!!!
 

Answer 2

The Timurids were descended from the Mongols,the dynasty having been founded by Timur the Great in the 14th century.Timur was a Turkicized Mongol.

2 main reasons:
Timur was a Muslim,so the Mughals were emphasizing their Muslim heritage.

Timur was a mighty warrior and conqueror,and much nearer in historical terms to the Mughals than Genghis Khan,so they were emphasizing their warrior heritage through a relatively recent example,and the founder of their dynasty to boot.Further,Timur had been a patron of scholars and the arts,and had constructed some awesome monuments (which is more than Genghis and his immediate successors ever did),so the Mughals were stressing a cultural heritage as well through being Timurid.