Wake Turbulence is certainly a possibility. The aircraft in entering its last turn exhibits an instability in roll that could be Wake Turbulence induced, but consider that for the instability to remain uncorrected points instead to the inherent instability of this a/c at speed. WT is a fleeting event, it flies its own path, and it does not conform to the flight path of the following a/c.
Was the Ghost In/Out of W/T? If the procuring cause of the upset, it is unlikely to have remained in the Ghosts path, and the upset/crash was a result of the initial snap Left, whether a broken tab, overcontrol, W/T, or STALL.
On the back straight, Ghost descends and levels, reaching its likely maximum speed in the circuit. The turn imparts high G force and the turn tightens as Leeward rolls to ~80 degrees.
Ghost is in passing mode, flat out, and the psyche is powerful. I think 177 is as tight to this pylon as any in the circuit, and loss of control at its most susceptible.
Roll Rate on this a/c is rapid, far higher than the factory model with ten feet less span. Similarly, the ailerons are half length, and it would be interesting to know if they were clipped Out/In, or In/Out. This is critical, since ailerons are airfoils, and subject to STALL just as any other.
So, maximum velocity, roll rate; minimum wing, aileron. Test Flight.