How did they gain X1/X2? Didn't Stagecoach operate the X32?
No, these are all commercial routes. X2 was formerly Oxford Bus Co (Oxford-Didcot), but was transferred within Go-Ahead to Thames Travel (and recently extended from Didcot to Wallingford); the X32 has, as far as I know, always been a commercial route and was originally introduced by Thames Travel a few years ago, and has never been operated by anyone else (it was recently extended from Chilton on to Wantage); the X1 is a new route that basically replaces the former 32 (which *was*, some years ago, a Stagecoach route, and more recently OCC-tendered before becoming almost entirely commercial) between Wantage to Abingdon (via a different route into Abingdon), and carrying on to Oxford.
As for what's going on? I think the short answer is that they introduced (in December) a somewhat ambitious, and very wide-ranging and (South Oxon) network-wide set of timetable changes that didn't in all cases allow sufficient time for some journeys, and for which they may well have had, at the time, insufficient resources. (Certainly the service for several weeks after the changes was consistently atrocious.) To some extent this may have been improved recently, with some buses being transferred from Oxford Bus Co, and with buses freed up by abandoning the Bracknell operations.
But, yes, there is evidently still further to go.