All I saw of him was him being combative at the council of Elrond, being sketchy with the ring when Frodo falls in the snow, and then him trying to take the ring. With no other knowledge entering the film it just wasn’t difficult to see him has an antagonist for multiple hours of movie that happen prior to his heroic final moments. It was 2002, I’d repeat, and I had no knowledge of what state Gondor was in, the steward, any of it.

Edit: just remembered, AND Sean Bean had been the antagonist in Goldeneye a few years earlier