Development costs doubled from 2 billion to 4 billion. Then when they went well over 5 billion and the federal government + Quebec had to bail them out to the tune of 1.5+ billion. Even without Boeing, had Airbus not stepped in, it's unlikely the CS100 would have succeeded. European buyers had already started to cancel orders seeing the debacle unfold.
Despite having many orders on the books, banks refused to lend to Bombardier because they expected them to make a loss on the airplane.
So yeah, screw Boeing who played really dirty and Trump helped them (the tariffs were reversed a year later when a more independent body reviewed them). But had Bombardier not been in a massive financial hole this wouldn't have mattered.