Perhaps their business model was past its useful life. Are the days of the cowboy (four major accidents and enough anecdotal evidence from other threads justify this description) freight operators drawing to a close.
Maybe the future of freight is with the likes of Cargolux and Aerologic. Well capitalized professionally run operations with modern fuel efficient aircraft as opposed to shoestring, rule benders with thirty year old junk.
Obviously with hindsight we can point to things which should have been done differently and the global financial crisis coming on top of record oil prices may have been the last straw. If the Halifax crash hadn't happened, if oil hadn't hit $140+, if Lehman Brothers hadn't collapsed, if B767 freighters had replaced the DC8s and B742s, who knows ?