As for prior attempts, their result is grossly overstated. Biosafety Now has published a detailed call for its retraction:
https://biosafetynow.substack.com/p/crits-christoph-et-al-20...
I don't think the details are really necessary, though. Approximately zero cases outside China were traced to their introductions, despite the forewarning, and despite the restricted set of options (an airport or seaport). This isn't for lack of trying--it's just really hard to do that from epidemiological data that's necessarily scarce and biased, especially for a virus whose frequently mild symptoms mean most cases never get ascertained.
So why would anyone believe they'd succeeded at the much more difficult task of tracing that very first introduction? The usual answer seems to be "because the paper was full of math that I didn't understand, and I trusted the authors"--but that's a pretty bad reason, especially when the authors are funded by and coordinated closely with the agency that advocated for (and funded!) the high-risk research in question.