Because there're arts from the very first artist who abandoned the project, and recently we started working with one more artist.
We're going to redraw some crucial scenes/arts from the very first artist so that they don't stick out like a sore thumb, but yeah.
I could just keep working with the main artist now but then it'd take ages to finish the game.
I don't think that artists I have right now have a drastic different artstyle, there might be differences but it's all to be able to release bigger updates in shorter time. I hope it makes sense. It's really hard to find two artists with a truly similar artstyle and unless I want to keep milking the game by releasing small updates (which I don't), I decided to look for one more artist.