How on earth is Apple TV a failure? It's a product they don't really seem to care about and they have the majority marketshare[1] (in 2012) and have been selling millions of the things each year.
They have had failures though, of course. Ping was another, for example.
Apple TV should be replacing cable set top boxes, the same way iTunes replaced music stores. It has yet to do that (Netflix has gotten closer than Apple has though).
It seems like they're moving towards it. They've been signing deals with cable companies and hiring people related to TV. It's certainly not an easy process, especially as people in TV are wary of Apple.
They have had failures though, of course. Ping was another, for example.
[1] http://9to5mac.com/2013/07/16/report-at-56-apple-tv-takes-ma...