India also has a billion kuffar (hindus, sikhs, jains, etc) besides I dont think Saudis will chose india over China because of Religion. Saudi Arabia is America's close ally and America has only 3 million Muslims and China has 22 million Muslims. Saudi Arabia will chose the next superpower and that is most likely China.
Well you didn't get my point. USSR had more Muslims that the US, but a communist ideology that completely negates religion is not compatible with Islam or any person who wants to follow their religion. Hence, the issues in Xinjiang or Tibet. On the other hand, the US openly enunciates freedom of religion.
Even Pakistan-China relationship is only because hostility to India. Otherwise the land route is uneconomical and the culture totally different. But more importantly their communist ideology that does not give freedom of religion will not go down with any practicing Muslim.
Who knows, maybe the Chinese will rid themselves of the Communist ideology in the future. After all, economically they are more capitalist than communist.