It was the mussies that captured and sold them into slavery and blacks continue to convert to islam.
The people that bought them, for the most part, were Christians. And after centuries of working in the sugar cane and cotton plantations at their owners will, their descendants still call themselves Christians.
At least the Muzzzies had the good sense to whack off the reproductive parts on the males they sold to the Arabs. Most soon died from the operation or died digging wells around Arabia.
Europeans wanted the ones they bought whole.