But it's not an appeal to popularity. The Dio and Ozzy eras are both more unique and well-crafted musically. Has nothing to do with popularity.
In the 70s and early 80s, Iommi set the trends. In the mid to late-80s, Iommi started to follow them.
I disagree here, last album where they weren't following the trends was Sabotage. Since then, they played what was "in". Technical Ecstasy and Never Say Die were prog/rock influenced and Heaven and Hell and Mob Rules were following NWOBHM trends.