One key thing not mentioned, is that Cheika in 2014 and Link in 2010 both inherited very good squads that needed some rounding out and some work on different aspects of their games to make them genuine contenders. I have long argued that the ground work for Link at the Reds was set by Mooney and the excellent backs play they had in 2009. For Cheika he in heirited a team able to play a statistically good game which gave Cheika very good foundations and a great squad to begin with.
To say that a new Head Coach (not to mention the support coaches also) come and miraculously turn it around in two seasons is a long reach. That is not to deride the impact that Cheika and Link had in their respective terms at the start, but they also benefitted from strong ground work strong starting squads.
I contrast that to Gibson at the Tahs who I have said from the start has been hamstrung by poor squad recruitment since 2015 and in his first year also had Nathan Grey as defence coach with that horrible shite defensive structure that saw the Wallabies with one of the leakiest defences I have ever witnessed in a Wallabies team. In judging his tenure this is his first real year of clear air and IMO the performance of the side has been very good in general, with some very good rugby played. Individual skill failures such as Foley's kicking from hand continue to plague but in the matters that Gibson can directly control I think the outcomes from my POV are very good.
This contrasts with Thorn IMO, who has developed and selected a very strong pack, which he largely inherited as the others did, but he gambled that this would perhaps provide enough of a platform that a rookie or journeyman 10, whilst both good players, could spark enough of a backline to win games. Much of the angst comes back to the mismanagement of the Cooper fiasco. Hunt and Slipper to a lesser extent I can understand. Cooper has no such public incidents in the last 6 or 7 years with which to justify this removal. This has left him open to the justified questioning of his entire approach and suitability for the role given the results and the fact that he has extremely limited coaching experience.