Sometimes artists can't keep up with demands so they can get dropped and hire new artists to continue the series after season 1 due to burnout. Artists also get injuries in their wrists from drawing and get replaced so they rest before the next project.
In this case I believe with the quick switch after season 1 they were contracted to do S1 and then someone takes on S2 to keep up with the updates to maintain its popularity or attract new readers...which I think harms the series as art plays a major part in attracting readers. It's happened a few times from beautiful art to "I will tolerate the art just to finish the story."
Ohhhh damn that really sucks, and thank you
Can anyone tell me why the artist changed o.o