After the Mongols wiped out Persia, they adopted Islam, and their descendents became the Mughals.
Only one of the four branches: the Ilkhans. In fact, this is fascinating....the Mongols were known for their religious tolerence. However, after conversion to Islam (Timur the Lame was the first prominent Ilkhanite), the Mughals became fully fanatical adherences of that pedophile prophet.
The other three branches of the Mongols (Batu's Golden Horde, Kublai's Sino-Mongol, and the Chagatai horde in Mongolia) retained their Mongol shamanite religion or adopted Tibetian Buddhism.