It probably was a perfect storm of errors. I do agree, that blaming the failure on "declining mall traffic" is not acknowledging the deficiencies of the business model. To state external reasons, is an attempted shift away from inner responsibilities. The error for them, was primarily an evolutionary one. They didn't adapt and evolve.
They didn't move fast enough in a high paced, technological world. They started in 1965 as farmers selling tools to improve productivity. It was a great mindset in 1965, but they didn't evolve much, past that point in time, or if they did, it was very slowly.
In the end, they became stuck evolution wise, somewhere in the 1980s. The death blow was the advent of computers and smart phones. As others have said, the Brookstone relevancy was lost. But instead of recognizing that, they resisted changed and stuck with old products, old ways of doing things. The chairs were a fail. 90% of them were inhabited 90% of the time by people with no intention to buy. Most visits to the store were by people intending to get a "free massage." Prices were out of touch with reality. 50% of a store's products were chosen by buyers who made poor choices.
In the end, Brookstone was appearing more as an old man whose time had come. Once unique, it was devoured not just by Amazon, but by Newegg, TigerDirect, Frys, etc, etc, etc. The writing was on the wall, years ago. This was a predictable event. It started in 1965, as I mentioned. It had its day.