You were probably remembering the old VGC estimates. Hugely overestimated Skyward Sword. I think something around 4.4M originally.
It then got adjusted down to around 4M but even that was not enough. Official shipment was only 3.67M lol
Guess the bad E3 showing and the Motion Plus requirement really hurt its sales, also it is a very divisive game in the franchise.
Yea and I feel like people got tired of the Oot formula after TP which was pretty much the best they good do with the system they had and the formula. I know they wanted to make more out of SS but the limited them and they had to release it for 25th so it ended up being a bit lacking in some aspects.
It is still a good game but yea it got hurt by the fact it was just one of too many games using that.
Some fans are complaining about the changes in Botw but like.. it was clearly not working out anymore. Some things of Botw are fresh and highly needed in the franchise. We'll have to see with the sequel what they keep and modify. But clearly the Oot formula is dead and it was about time.