"Support still there? where is the screwjack?"
The fuselage rear assembly is the support, it is present at the crash. Turning 90 degrees is impossible as it was still attached a 2 of the 3 HS mount pins if you screw assy is disconnected.
With the pivot points still attached, the fuselage forms the range of movement limiter
Had it gone 90 degrees, there would be nothing left at all aft of the RPB.
Go look at the construction photos of the HS being mounted to the fuselage rear. Your scenario is not supported by the physical evidence at the crash site.