As I said, that was merely the first of many. And there is no such thing as "virality" - see my answer to the sibling to your comment.
The "enforceability" of the GPL was never in any doubt because it's not a contract and doesn't need to be "enforced". The license grants you freedoms you otherwise may not have under copyright. It doesn't deny you any freedoms you would otherwise have, and it cannot do so because it is not a contract. If the terms of the GPL don't apply to your use then all you have is the normal freedoms under copyright law, which may prohibit it. If so, any "enforcement" isn't enforcement of the GPL. It's enforcement of copyright, and there's certainly no doubt on the enforceability of that.
For the GPL to "fail" in court it would have be found to effectively grant greater freedoms than it was designed to do (or less, resulting in some use not being allowed when it should be, but that's not the sort of case being considered here). It doesn't, and it has repeatedly stood up in court as not granting additional freedoms than were intended.
Look at the "many" if you want to cite better cases about this.
I've cited further cases elsewhere in this thread. If you'd like to test this yourself feel free to repackage some GPL software as closed source, flog it to people and see what happens. I'm not your lawyer.
https://news.ycombinator.com/item?id=46070191
I see more discussion in the sibling thread, but I am still waiting for a case actually relevant to the virality of the GPL. The article is about how use of GPL code can "infect" LLM weights and force their disclosure, and I am personally somewhat doubtful that is legally the ccase. I am also further convinced that this theory has never been given real legal force.