This is normal.
Below is Wisconsin Lakes’ lakekit.net service provider’s (Ken) explanation:
“if you are viewing an image that is not assigned/attached to a page using the “view attachment page” link in the media library you should be redirected to a 404 error as the image is not assigned to anything as of yet.
When you view an image that is assigned/attached somewhere the link terminates properly and you view the image on the page it resides on.
The alternative action is to click on the “original image” link which will bring up the image in the browser from the upload folder the image resides in.
I hope this helps.”