The first year the Grammys recognized "Hard rock" performance was after 1989. After the "incident" was when they came up with best metal, alternative etc...categories because of a little controversy & a lot of criticism
That first year of the Hard rock performance in 89 the nominees were: AC/DC, Iggy Pop, Janes Addiction, Metallica & Jethro Tull. Basically Janes & Iggy were recognized, rightfully so but also weren't really "metal" or "hard rock".
Everyone expected Metallica to win.
When they announced Jethro Tull as the winner everyone at the awards show booed.
Grammys are a joke & nothing but a popularity contest. It has nothing to do with recognizing real artists or good music.