As artists grow, they often dislike their older artwork.
The new redesigns are because Nuria, the same original artist, had things she disliked about the original designs that didnt fully fit her vision for the game and as time has gone on looking back at one's own designs you start to dislike them anyway.
Plus with this update, the animations can happen! Its a net positive, and the style hasnt changed, merely the artist developing as all artists do.