" If it was that bad, why did anyone buy it? They may not have foreseen its unreliability, but poor performance would have been a known factor surely"
Nobody really bought the heap of scrap, Waste of Space virtually gave the heaps of junk away in an attempt to enter the turbo-prop market.
Trying, and failing with outstanding ease, to use Boeing's practices of developing a known airframe and systems, the result was a freak of aviation.
Product support was useless, but it was an accountants dream with a 650 kg fuel upload from say MAN to GLA . BFS etc and only a very small pax load to make a profit.
A testimony to every budding design engineer as to how NOT to design an aircraft