What they did is that they filed a provisional application in 2006. This is not a patent, it is just a simple way of saying "I did this". This way, you can rele

What they did is that they filed a provisional application in 2006. This is not a patent, it is just a simple way of saying "I did this". This way, you can release your invention and apply for an actual patent later without the risk of having it rejected for prior art. A provisional application doesn't grant you exclusivity, only the right to file a patent later, where later normally means less than a year. Then Sonos filed a patent in 2018 based on that provisional application, well after that reasonable 1 year delay. By the time, the industry has built something based on that 2006 non-patent. Essentially, Sonos tried to patent the thing retroactively.