Between him and Blue Öyster Cult, they gave the Satanic Panic a life of it's own during the 1980s.
Although there was a great deal of Satanic imagery, there was nothing that was ever written or sung overtly in "Praise of Satan" - not even N.I.B ("My name is Lucifer, please take my hand").Can't say I was ever a fan, really. I recognize Black Sabbath's influence on music in the 70s and 80s, but the only metal band that ever really did anything for me was Metallica.
First I ever heard of Ozzy was around 1982-3. Not long afterward there was a local controversy in advance of his tour date in Sudbury on the Speak of the Devil tour because of his supposed Satanism and his stage antics (i.e. the infamous bat). He did his best to assure people he wasn't really a Satanist and he prayed before every concert, and according to the news reports of the time, he closed the concert with "God bless you."
A decade earlier, Sabbath bassist Geezer Butler, a Roman Catholic, had written the song "After Forever" (co-written by other band members) to try and dispel the band's Satanic image. The lyrics are, in a manner of speaking, evangelistic.
Ozzy was indeed no Satanist, or even an atheist--he was at least a nominal member of the Church of England, and it was probably entirely true he prayed regularly. Was he a believer as we would understand it? Probably not. But even in a liberal Anglican church, the Gospel is read regularly. We can at least hope that if Ozzy knew his life was coming to a close, something of it made an impression on him.