Speaking to Kerrang!, Iommi recalls that Sabbath's prospects at the time were "dismal", and that it was actually Sharon Arden (later Sharon Osbourne) who introduced him to the singer who would replace her future husband.
"Things weren’t happening, and Ozzy really wasn’t into it anymore," Iommi recalls. "He was going through a lot of stuff at the time. And we had to either break up or replace him, which we didn't want to do. But it got to that.
"I met Ronnie a party probably a few weeks before that, and it was Sharon [Osbourne, then Arden], who introduced me to Ronnie. I actually talked to him about doing a side-project ourselves, something a bit different with the both of us. And he was into that. And then when Ozzy went, the first person I got in touch with was Ronnie. I said to the other guys, ‘Why don’t we try Ronnie, and see what you think?’"
"Ozzy was great, but Ronnie was a different singer altogether. We wanted somebody who was different, we didn’t want to bring somebody in who was gonna sound similar to Ozz. So it was good to have somebody totally different, and Ronnie’s voice and the way he approached the songs allowed us to be able to try different things in a different way than what we’d done before. It opened up a lot more variety for us, really... It gave us a new lease of life."
Earlier this year, Wendy Dio, RJD's widow, said that her husband received a rough reception from a section of the Sabbath fanbase when he joined the band.
"He got spat on and he got booed," she recalled, remembering how it was "very hard" at times for her late husband.
"Ozzy, when Ozzy was on top form, was one of the best frontmen ever," said Dio, as transcribed by Blabbermouth, "When [Ronnie] went into the band, the music changed a little; it was more melodic and completely different."
"I've always said: there's Black Sabbath [with Ozzy] and there's Black Sabbath [with Ronnie], and they're both as good," she continued. "One is not better than the other; it's just they're different — they're totally different
"I mean, Ozzy was an innovator, and that's music that was the innovations of the start of heavy metal, and I would never put that down. But Ronnie made a difference; he was different... And then I think the kids started to really accept him."
Reissues of Sabbath's Dio-era albums Heaven And Hell and Mob Rules are out now via BMG.