I’ll throw my hat in. In companies like DC and Marvel, they have a lot of series going on under one company. They rotate artists sometimes to keep things going, unlike Unlike CLAMP, a japanese manga company, who stops series to start new ones instead
Usually they try to pair up artists and writers, and switch those up frequently basically for variety. They switch the artists more often if the art is not selling well or the artist has some sort of conflict.
It’s hard for them to keep up the pace they need to, sometimes. And when writers change, artists change as well. Or when a book isn’t selling well, they put better-known artists on it to boost sales. You typically get one artist per story arc.
American comicbook artists don’t get assistants on their work and they have to draw 30 cleaned and detailed pencil panels (usually with detailed backgrounds) ready to ink per month. It takes a toll on them.
Generally comic change artists with writers. Or sometimes the editors decide to “freshen” the story with each new arch that shows up. It’s rare to change artists in the middle of a plot, but if they do the styles tend to be very similar.