I'm not sure they struggled any more than anyone else with WLTP? Remember, WLTP is only the drive cycle. The actual emissions limits (tailpipe emissions of chemicals like CO HC, NOx, and particulates, not CO2, which is separate) were set out in the various "Euro 6" regulations. It was all quite simple, with the limits changing for Euro 1 Euro2, 3, 4 and 5. But the VW scandal broke during Euro 6, so the EU Parliament gave the EU Commission a right kicking and told them to get a grip on it. The Commission responded by rushing-in several different versions of "Euro 6" (Euro 6a, 6b, and so on). Even worse, we had "Euro 6dTemp" and then "Euro 6d" - which is what we're on at present. The next one (we're told) will be Euro 7. It gets incredibly complex and I'd have to fire up my "work" laptop to find which changes went with which letters. I've a feeling WLTP came in with Euro 6d Temp and RDE but with fairly generous "conformity factors" (i.e. the manufacturers were allowed to exceed the regulated limits by a small "conformity factor" when tested on a real road, in recognition of the fact that such a test could never be as repeatable as in the lab). I think Euro 6d brought down the conformity factors.
I hadn't heard anything about tuners tipping-off academics, but yeah, maybe that's true? I was under the impression that it was students in Virginia, looking at city air quality and comparing it to what it should theoretically have been for the traffic concentrations, if all the vehicles had been emitting according to the regs. They found a surprising disparity. However, as you say, it's not that important who broke the story!
I don't really get how you can "conspire" to have a bigger AdBlue tank? They just needed bigger AdBlue tanks to meet the NOx requirements! VW could have done that too, but diesel isn't popular in the USA and the European manufacturers (especially VAG) had really pushed "clean diesel" technology very hard over there. They were just starting to get somewhere, when the regs changed to require AdBlue, and (at least in the story I heard), they were worried that American consumers wouldn't accept having to top up an AdBlue tank, so they tried to size it so that it would only need topping up during services. This meant having to reduce the dosing to make the contents of the tank last long enough. Unfortunately, reducing the AdBlue dosing, also meant that the cars emitted more NOx than they should have done. Accordingly, they came up with the idea of giving the car the required amount of AdBlue only when it was on a rolling road (using the steering angle sensor to work out that the car was being driven but not steered). However, none of that explains why they then decided to do the same thing in Europe! Certainly, over that period, my company cars were a series of 2 litre (150 horse) Sharans and it was very noticeable when they became compliant, because the AdBlue consumption practically doubled on the later cars!
Skoda were using the same "cheat" for NOx and AdBlue consumption as the rest of VAG, I'm afraid. However, they might not have known it, because they buy the technology from VW, but even on their own website they admit they were:
https://www.skoda.co.uk/owners/ea189-claim
CO2 is a separate issue entirely. There was never a regulated limit for CO2 emissions "per car". It was only ever a fleet averaging requirement.