I think, trying to be objective here (and I know, people are not going to trust be to be remotely objective given the subject matter), but I think there is an element of nobody being willing to go after Kuss' advantage because they'd have to answer to both Vingo and Roglič who would be able to follow and stay fresh anyway, so it was a hiding to nothing (plus the - at least initially, but as the race wore on, increasingly forlorn to the point of being totally worthless - hope that Kuss being in red could foment a bit of internal rivalry in the team that somebody else could profit from), but the whole "GC Kuss" thing was lightning in a bottle with the race win thanks to the other two being told to knock it off and play nice for PR reasons, and ended up being a poisoned chalice.
In some respects you could say that Sepp Kuss the GT contender has been rather more like a better version of Óscar Pereiro or David Arroyo when they got their time gift-adjusted successes. Pereiro was a class rider who had been 10th in the Tour in both 2004 and 2005, on the podium of the Tour de Suisse in 2003, and was only half an hour down because he'd dropped time to stagehunt. He only had a minute and a half from Landis, and held on to the final TT, but he didn't have anything like the support team Kuss had, with Valverde crashing out early, and Karpets and Arroyo his top helpers. The following year, operating as a GT leader with the #1 on his back, he finished... 10th (after the DQs). Right back where he left off. Likewise David Arroyo had been 10th in the Giro twice (2009's later upgraded to 8th) before his 2010 odyssey thanks to the time gift - and then when he went into the race as leader the following year he finished... 13th.
Kuss has managed GT top 10s and multiple top 20s before his surprise run to red last year, but they had largely been as a second- or third-in-command, and part of the current trend towards super teams where if you want to do a good GC but aren't a genuine victory threat, it is better for you to be a superdomestique in a superteam than a leader of a weaker team, as seen most obviously in this year's Tour de France where UAE put domestiques in 4th and 6th, and Soudal and Visma put domestiques in 5th and 8th respectively. That's how Sepp's only other GT top 10 - the 2021 Vuelta - had come about, elsewhere his best successes had come when he was relied on to stagehunt to salvage a race when the leader crashed out, like his stage win in Andorra in the 2021 Tour. Asking him to act as a sole leader aiming at the GC was always going to be a tough ask. Maybe if Pogačar hadn't gone for a Giro-Tour double and Roglič hadn't had to pull out of the Tour, it might have been a different story. Maybe if he'd stayed healthy early season and got some confidence-boosting strong results prior to Burgos to give both the team and himself some faith in his ability to perform as a leader, it might have been a different story. But instead, it looks very much like a tale we've seen many a time, of a strong rider finding themselves in an unexpected advantageous position and performing up to the level of the position, but then not being able to replicate it when their card is marked, whether it be audience expectations, whether it be being taken more seriously by the opposition, whether it be a change to internal team dynamics or a collection of all of them.
The question will be, whether this was a learning experience and he can then establish himself as a credible threat as more than a fringe GC rider and mountain stagehunter (think something like Rafał Majka in the mid-2010s perhaps?) and become more than a one-hit-wonder to become a legit GC threat, or whether he goes back to his superdomestique job, maybe Visma bring in another leader or jump Jorgenson or Uijtdebroecks above him in the pecking order and it's "GC KUSS: The SQUIB is DAMP" forevermore.