What really doomed it was the proliferation of small airports where large planes can easily land (737NG or Airbus's own A321). One stroke of business genius on Airbus's part was buying the share in Bombardier - the A220 is gonna see massive usage in Europe).
Airbus really played on the whole spectrum - the company is well positioned on all segments of the market. Unfortunately the market is dwindling, and this marvelous piece of engineering is dying. I only hope I'll get to fly one before it retires.