The 2015 maker market is
tiny compared to the 1985 one.
In the the UK the 1985 market was big enough to keep a handful of magazines in comfortable five digit sales, and an area of London - Edgware Road - had a component store ghetto where you could almost any part you wanted. (The tiny selection of components sold by RadioShack at ludicrous prices compared, to the epic lists offered by the ghetto shops, made RS a bit of a bad joke in the UK, even back then.)
There was almost no difference between 1985 product tech and 1985 hobby tech. In theory you could build almost any product you could buy out of standard parts, so there was always the incentive - or at least an excuse - that DIY would save you money. (Some people built amazing things to save money.)
In 2015, there's no way you can build an iPhone, a laptop, a games console or an MP3 player from scratch with a soldering iron and a bag of parts.
(If you look at Elektor, one of the surviving hobby mags, you'll see it's full of complicated, difficult hobby projects by full-time engineers. You need a lot more than a soldering iron and a cheap meter to build them.)
Bottom line is that the Arduino/Pi/Beagle/etc microcontroller market is nowhere near the size needed to keep a huge chain like RadioShack profitable.
And there's enough competition in consumer electronic sales to make it almost impossible to offer any other USP.
Add toxic management to the mix, and I'm amazed the company lasted as long as it did.
I won't miss RadioShack. I hope some smaller mom&pop enthusiast stores take over some of the same space - and that they treat customers and staff with much more respect and affection than RS ever did.