I kind of assumed (from a largely ignorant perspective) that this was part vanity/pork project as yu say, but that the real underlying purpose was to either simulate nuclear explosions for the DoE or to synthesize stupid large AI models with a trillion variables.

If the people in charge of this thing had an epiphany (or a blackout, take your pick) and left you with the keys for a year, what could you do with this inefficient but impressively large cluster, besides anchoring your paperwork?