Interesting one, I expect there was a lot of politics about it but that aside, in terms of airframe design, it had four engines which is a bit unnecessary on a regional jet, twice the maintenance cost for enigines, not to mention fuel costs post 9/11. Although it had very good STOL performance it had relatively poor performance in terms of cruise compared to small airbuses and embraer etc. Although I am prepared to stand corrected on that point.
Sept 11 was the final nail in its coffin I fear, with a very thin order book and increased competition from the Embraer 170/190 market to name one plus the A318 and Bombardier aircraft, BAe were making a loss on each aircraft they sold with no prospect of further orders.
A real shame, as it was a proven design which was popular with some airlines and had also got some US interest, albeit small.