They haven't. I may not agree with who wins, but I'm not gonna run around crying foul saying it's "rigged" because of it. I guess that sense of understanding comes with maturity. Not everything goes the way you think it should.
But I feel like the Grammy's do still have some credibility when looking at their other nominations other than the pop categories (which are largely given to popular songs rather than good songs / albums).
Like A Prayer not getting any nominations in 1990 I find it unacceptable to snub the album that is as close to art as pop music gets. At least the era got a Grammy for the Blond Ambition Tour in Best Long Form Music Video.
They haven't but just like every other award show,they give the award to people I might not like or agree with but the end of the day,there's still credibility.