I think a big part of the reason there's so much hype around this is that room temperatures superconductors have long been a famous, almost legendary undiscovered material in popsci. Theoretically possible, but with no proof that any such material actually exists. But now not only is this paper claiming that such a material exists, but also that they made some, and it's easy to manufacture and works at temperatures well beyond ambient. Seems almost too good to be true!

So in addition to any immediate practical applications there's also this element of cracking a famous long unsolved problem. It'd be like if we discovered definitive proof that P != NP, or a theoretical basis for FTL communications. Even with no immediate practical applications it'd still be huge news.