At this point I'm sure it's deliberate. The only thing I can think is that this is the natural cycle of changing government, there's nothing more they can do, everything is fucked and beyond the point it can be fixed. So rather than lose on the merit of the party (which is in disarray and has achieved nothing other than lining their own pockets), they can pin it on Sunak who can happily retire to California on his millions. I assume he's cut some kind of deal to retain support beyond his premiership and this is all just performative.