The C-Series is a fail
Don't be so certain. At the time of first flight of the prototype CRJ in 1991 Bombardier had one firm order (from LH) for thirteen aircraft. They are now closing on 2,000 units produced as the CRJ created a new segment by filling a hole in the market.
The same will happen with the C Series - it will fill a significant gap between 100 seats and 150 seats.