All cameras looking the same way despite being directed another way I have a simple scene with two starships organized into two collections, and two cameras, each camera looking at one of the ships. 

In the course of creating this scene, I must have done something that results in this: all the cameras are now looking at this single ship, even though they are really directed another way, as you can see on the GIF below. In the GIF, I am hitting the 0 key to switch to the view of the selected camera.

There is no constraint (like Track To, for example) applied to the camera. The camera that should be looking at this ship is animated and has a noise modifier applied to it to make it shake. This is also affecting the second camera that should be looking at the other ship, which is also shaking.

What could be causing this?
The camera you refer to, isn't the active one. Press Ctrl+0 to set the selected camera in the viewport as 'active' or make it the actual scene camera under Properties > Scene > Camera, which is basically the same.

Tip: The triangle on top of the 'active camera' is filled up with a solid color.

Manual: https://docs.blender.org/manual/en/latest/editors/3dview/navigate/camera_view.html