Why does everyone hate Russel Crowe’s singing?

I have been obsessed with this movie/musical (both 1998/2012 since highschool when my French teacher made us watch this movie in French. I’ve lately been watching the 2012 movie, and I think his singing isn’t bad at all. I think this movie from a filmmaker/videographer’s perspective is so beautifully done. The actors, the singing, the visual affects, camera angles it’s an amazing film.

But reading the Reddit thread everyone is saying they hated his singing performance…