Somewhere in that process they made a copy of the image. They had to - there's no way to read an image file and not have a copy somewhere on the computer that you're reading it on. Even if it's just in the RAM and it never touches a disk.As I understand the technology, midjourney at least does not copy images. It reads patterns in them on a pixel by pixel basis and connects that data to key words. Note that I am not defending the scraping, just explaining the difference.
Our entire Web usage has skirted around the issue of copyright and the fact that browsing the web necessarily means making copies of everything we view on it. We've all kind of chosen to ignore it because it wasn't in anyone's real interest to try to figure it out - if I post something for you to read I want you to read it, and if that means you have to download it to your machine to read it, well, then I'm implicitly giving you permission to do that just by the nature of the technology.
Does that mean that I'm also giving you permission to use the same text/image to train a neural network to reproduce things in my writing/art style? I wouldn't think so personally, but that's a question of law that needs to be figured out. And I personally hope they resolve it correctly and say "no, that permission was never granted, pay them for the right to do that or don't do it."