Most of the stuff that the DIYers needed was not inventoried anymore. From what I can tell, they sold batteries and phone accessories like cases, cords, and earphones as well as some R/C toys. They didn't really have an identity anymore.
Most of the stuff they had on the shelves were just kind of curious items that were once in a while replacement things like button cells, but the prices were so outdated, like $5 for a single LR44. No wonder they collapsed.
I don't think RS did anything wrong, but they should have turned into a Best Buy kind of place. The core market for their identity, DIY and ham radio is dead.
Most of the stuff they sell is available online for 1/10 the price they charged shipped to your door. The market changes. People buy TV's and audio at Best Buy. They get their DVOM from Harbor Freight for $3.99, not RS for $32. I guess even car audio is dead for them since they don't install.
I guess they just weren't able to adapt to a changing marketplace.