You would literally have better results asking what went wrong. TCW (especially the later seasons) is the best animated action show in recent memory by a comfortable margin. Far better than anything that was airing at the time or has come since. So much so that even its own direct fucking sequel can't hold a damn candle to its shine.
Everything from its look
>supreme settings, backdrops, scenery, lighting, fight scenes, effects, and character/object designs
to its sound
>excellent voice acting and casting, sound effects are authentic to the movies or the original ones at least sound appropriate for the universe, great fucking soundtrack
to its characters
>Anakin's arc from the annoying shithead we know him as from Episode II, to a decent fucking hero and an actual protag you'd root for, to his slow, subtle pull to the darkside
>Supporting cast - Obi Wan, Ahsoka, other jedi, the clones, GG, Ventress, Cado, even Padme was done "right",
to its plot
>Order 66 arc
>Ahsoka betrayal arc
>Highlights of the Maul/Opress arc
>The jedi who bretayed the clones
TCW is a fucking masterpiece that should be studied, a fucking mandatory 301 course for anyone in the action animation business.