By 2382 they have either achieved an insanely high technological level, non-corporal form and maybe the possibility to somehow realign their planet to the rest of the universe or extinction due to war. I hope it's not the extinction thing.
Not necessarily extinction due to
war, if that's any better; it could've been natural collapse of their civilization. I mean, they were at 1 of their days every 1.03 seconds, and it's been about 6 years between that episode and 2382, that's the equivalent of
about 500,000 years for them. (With some variance depending on the "natural" length of a day on the planet, of course; probably anywhere between 250,000 and 1,000,000.) A single civilization surviving that long continuously would be very unlikely even in Star Trek, especially one where off-planet resource collection wouldn't be possible at a feasible rate from the surface perspective.

(Though I suppose it could be the civilization collapsing without extinction, then a new civilization rising, etc. Honestly, in 500,000 years, that could have happened a few times.)
I'd prefer to think non-corporeal form too, myself. Or maybe evacuation?