Heroes' Path: a design post-mortem

I'm curious why the art style changed so drastically in the second expansion, "Tribes of the East"? This mainly concerns the drawing of the units (not their 3D models, but their avatars). It seems like a different person drew them. For example, let's compare the first upgrade for the Elves with the alternative one. The first one is so delicate and refined, so fantastical in its design, while the second one is crude and almost carelessly executed. The Dryads have blue, puffy faces, and the Wind Dancers have giraffe-like necks. Why was it necessary to change the art style in the middle of the game, and why change it for the worse?