My guess is the same reason the final episodes of Black & Gold were also taped, i.e. they need additional time to reconfigure the CWC/NXT Arena/Performance Centre/whatever else you want to call it.
It was reported on Fightful Select that there have been pitches for Rhea and Ciampa to be part of Edge's stable, although no confirmation that either of them actually will be.
I'm not sure any of the matches on night two of Mania can possibly be as bad as the match I've just watched between Blues and Albion. That was a waste of a tenner.