Did Genghis Khan have a religion or did he commit atrocities for another reason ?

What atrocities?

Chingis Khan carried out a war of empirial expansion -- but all in all it was done according to the rules of war.

Regarding religion --

Chingis Khan's philosophy of religion was reiterated by George Washington and is enshrined in the First Amendment of the American Constitution.

To whit -- that all shall have the right to worship according to their concience while their behavior is in conformance to the interest of the nation.

Under the Chingisid empire, freedom of religious worship was guaranteed and religious institutions equaly protected from taxation -- under threat that a governor who was found to have opressed any religious group would be flayed alive.

Chingis Khan himself was a religiuos man -- a Tengrist Shamanist - and he did believe that the Great Spirit had destined him to unite the world under his rule.

Although a bloody warlord Genghis Khan allowed ALL religions to be practised freely in his dominion and also in his capital. This was a major gain for his empire, as the europeans expelled several leading scientists for not being chrsitians enough who then moved to his capital. His closest circle included animists, christians, muslims, buddhists.