This is why we need to scrape services like this and keep copies for posterity. For every site like this that can't sustain itself well into the future, a part of the Internet and its culture dies. RIP Soup.io
OP may have a different answer, but the Internet Archive[0] and the /r/DataHoarder[1] communities are really obsessed with digital archival and preservation. The latter has gone to great lengths to, well, hoard anything and everything imaginable that they can.
Doesn’t the Internet Archive have a collection of websites they backed up just before they went down? Do they plan on backing up Soup.io? Do they even know about it?
The "Imperial We", obviously. Goes along with "someone should do something ...".
It's true it would be nice to keep copies for posterity, but it's not realistically possible to archive everything created for all time.
OTOH, state actors like the NSA should be archiving lots of things like this, because "you never know ...". But, unfortunately for us, a meme from years ago nailed this: "My computer hard drive crashed. NSA won't send me their backup copy."