It looks like you have all four views set to use your camera. Notice the white tick to the right of the camera in the object manager? That means the camera is active. When you’re changing the view projection you’re actually changing it in the camera, and since all four views are using the camera … they’re all changing together.
So instead of changing the projection (e.g., perspective, front, etc.), go into the camera menu, use camera, and switch it from the camera object to “Default Camera.”