*Speculation only*
Sometimes private schools are gifted donations but they have to be used in certain ways. I.e. Some old rich alumn
dies and leaves a big check but it's for a specific purpose.
Or maybe the upkeep on the old facility was a lot and it just makes sense to build new?
Could be several explanations.
Edit -
Looks like they are undergoing a large capital project that's touching lots of areas. I suppose it (and other projects) are an investment to reverse enrollment trends - or grow tuition base. Maybe they felt facilities aren't meeting demands for the tuition.