It would have been worse surely had Cormack been speaking to potential managers while McInnes was still in place?
There's every chance McInnes was told he could remain until the end of the season and declined. Cant imagine it'd be much fun going in front of the media to explain you've been sacked but are carrying on, likewise the players might lose respect for you. He also probably doesn't want another fourth place finish on his record.
If it is Glass, then Aberdeen have actually moved very quickly here. Compare that to Hearts and how long it took then to get Daniel Stendal, Rangers when McInnes turned them down and they went the rest of the season with Graeme Murty, and Celtic who sacked Lennon a week before McInnes yet appear no closer to appointing someone.