I suppose the weird surprise lesson of the Windows 8 fiasco is no matter how badly they bollixed it up, they wouldn't lose enough customers that they could afford break a lot more of the user experience than they ever originally thought.
Even Vista, while people had issues*, still provided a largely familiar interface and didn't go out of its way to break muscle memory and traditional workflows.
IMO, Vista wasn't as bad as is commonly held. A lot of the problem was that it was more resource-intensive than previous systems-- it really asked for decent graphics cards and 2Gb memory, but they sold a lot of cheap machines with 512Mb and crappy shared-memory chipsets that only qualified as "Vista Basic Capable" so that the manufacturers wouldn't have to formally declare them obsolete. Some drivers had teething trouble, but switching to 64 bit was going to have growing pains anyway.