First, Black Sabbath reemerges with Ronnie James Dio on Heaven And Hell, reviving their fortunes and giving them a new lease on life.

Second, AC/DC reemerges from the death of Bon Scott with Brian Johnson assuming the lead singer's spot and releasing their biggest album ever, Back In Black.

Third, Yes replaces Jon Anderson with Trevor Horn, for the not so commercially successful, but musically strong album Drama.

All great albums that still hold up 30 years later. Too bad Ronnie's not with us to celebrate Sabbath's milestone.

I'm not even remotely a fan of there's, but didn't Iron Maiden do something similar?

Yeah, but it was a year later, I believe. Number Of The Beast came out in 1982, so it was probably 1981 when Paul Di Anno got sacked or quit Maiden.

It was-after Maiden's 2nd album.
1980 also saw another major change in the singer department when Midge Ure took over from the departed John Foxx in Ultravox. Overnight Ultravox became a worldwide sensation (although only a loyal cult following in the US) starting with the Vienna album that year, and were part of the New European explosion. I love the Ure led Ultravox very much, but the Foxx era which was quite different was also good-just a little out there and totally unmarketable.