They didn't have to hit the cell phone market, as hard as they did.
They could have done fine with phones, TV's, stereo and surround sound, and other things that the average consumer is interested in, plus kept the random kits and components that hobbyists were interested in.
The Radio Shack locations that I've visited over the past 10 years, always seemed to have plenty of folks walking through the door. Not many of them, from what I saw, had much interest in cell phones, that day. They always seemed to be asking for some random electrical thing that a Radio Shack SHOULD carry, and it used to be, they did.
Also, it probably didn't help that Radio Shack seemed to have gotten insanely overpriced, on a lot of things.