[douche]

It's hard to find an era that doesn't have huge acts. Led Zeppelin, Black Sabbath, Kiss, Aerosmith, Lynyrd Skynyrd, ZZ Top, Deep Purple and more stretch through the 70s into the 80s, leading into AC/DC, Van Halen, Def Leppard, Motley Crue.

It's more of a niche now than then, (and maybe I'm ignorant of developments outside of the harder rock zone) but there a still big rock bands now; The Black Keys, Godsmack, Tool, Avenged Sevenfold, Chevelle, Disturbed. They may not be Beyonce or T Swift, but they can sell out arenas.

[ChemicalWarfare]

I highly doubt that any of the bands you mention in the 2nd paragraph will sell out an arena by themselves. Even in their heyday godsmack,a7x, disturbed would maybe fill a large club. But then once the "real metal" picked back up 10 years ago or so these bands lost their appeal to the old school slayer/pantera audience just because there were other "options" available. Same goes for the younger deathcore/metalcore crowd (with a7x managing to stay afloat in that pool but nowhere close to where they used to be popularity wise).

[serge2k]

The black keys are pretty mainstream compared to the others.