Just look at AdaFruit Industries and Sparkfun. These two companies couldn't do a better job marketing to the DIY audience and have done an incredible job expanding the reach of DIY, but even taken together, with MakerFaire thrown in, I don't think they'd crack $200MM in revenue. Topline. Assuming margins of 30%, it's a great catalog business, but not one that can support a 7,000 store chain.
The reality is during RS's heyday, if you wanted electronics, you had to build them. Or at least know the rudiments of repairing them. Today, the stuff we get from Shenzen is just too good. Too advanced and too cheap and too disposable.
While experimenting with Raspberry Pi boards is cool, it's a hobby, or educational experience, not a replacement for manufactured goods.
Changes in manufacturing took away RadioShack's raison d'être. Big box retail applied purchasing power leverage to take away many of RS's most profitable categories and Amazon/Walmart piled on. This left them as a weird Frankenstein combo of a Brookstone and cell phone retailer. Selling a few more Arduinos and Zigbee breakout boards wouldn't have saved them.