Microsoft released windows tablets with the mindset that people would want to do the exact same things with a tablet as they would with a desktop or a laptop. That's where they got it wrong. Apple realized that a tablet should be a consumer device and not a replacement for a laptop or desktop. A tablet would require a different operating system, not the one running on computers.
Microsoft envisioned the tablet as a full fledged PC and designed it in such manner. This made the windows tablet expensive. Apple took advantage of all of these, came up with an iPad that is way cheaper than a windows tablet and it runs an operating system that this not similar to a desktop or laptop. That's why windows tablets failed.
The reason that the Windows tablets failed was that Apple was producing way more quality tablets and they were able to market and advertise the products on a more effective scale than Windows and Microsoft did. Microsoft was betting that with the Windows name being attatched to a tablet that it would be a surefire way that would increase sales. That was far from what happened. The thing is that the Windows operating system can be found on all kinds of other devices and not just an exclusive Windows tablet. The company got into the market at the same time when all kinds of innovations were coming to the word of tablets. While some of the features of Windows tablets are around today, the Windows tablets failed miserably. The reason for this was that Microsoft was hoping and banking that consumers would focus on the Windows exclusiveness of a tablet. People found out that Windows was a operating system and not one that should be tagged with a tablet.