No, nobody knows - except those who went.
Likely explanations are:
Thrustmaster still holds the rights for live events
Fanatec was too busy to provide support, due to being at Spa-Francorchamps to support the Fanatec Esports GT Pro series and the SRO Esports Sim Racing Night
There's literally not enough GT DD Pros available right now for all 12 rigs, at least a dozen practice rigs, and spares in case of failure.