Perhaps.
But as someone who tracks the Oscar races regularly, there has been PLENTY of mud slinging over the last few years amongst major nominees. A Beautiful Mind was bashed heavily right before the Oscars in an attempt to bring it down, there were feeble, thinly veiled competing studio attempts to bring down The Return of the King (campaign quips like "Mystic River's only special effect is brilliance"), and there was the mentioned incident regarding Zellweger. This has been an issue for a while, in major categories (Best Picture, the acting categories) especially.
Was the third LOTR film WAY better than the first two or were the films in 2001 and 2002 that much stronger such that LOTR didn't win major nominations for films produced those years?
It is a fair question. There has long been a Hollywood bias against SF/Horror/Fantasy genre pictures. Back in 1986 Dennis Hopper was heavily talked up for Blue Velvet. He got nominated for a smaller role in Hoosiers instead. He had cleaned his life up and it was a pat on the back. Frank Booth was too unfriendly a character to be nominated "best" anything. Fast forward a few years and Anthony Hopkins wins for a role as a cannibal serial killer in Silence Of The Lambs.
Times change. Some in Hollywood detest that sort of film (and not just because of the grue). Why should "old Hollywood" types be silenced in their championing a different film?
Meanwhile there are still attempts to revoke Michael Moore's Oscar although I don't ever see that happening.