My understanding is routine runway inspections are co-ordinated with ATC in advance and for the arrival runway an appropriate gap is provided for the inspection teams (two vehicles, one from threshold to mid-point and other from mid-point to end) to carry out the inspection on a sterile runway without going on/off between movements. One of these normally occurs mid-morning, so given the take-off times were much earlier I doubt a runway inspection was the cause of the inbound holding as there would not have been the need to carry out an extra inspection for this event. I can only think that the inbound holding was so that ATC could ensure the aircraft using the arrival runway for take-off had a sufficient gap in arrival traffic so, if necessary, it could wait on the runway for a few minutes until the aircraft on the other runway was lined up ready for take-off.