If SpaceX has to step in to get the astronauts, Starliner will be scrapped and written off. Boeing has no benefit of the doubt right now. No one will assume this is a singular incident, and will be viewed with all of Boeing's other troubles in mind. Boeing needed this to go without a hitch, because they aren't trustworthy in the public's mind and NASA can't be seen as continuing to put lives in danger after the retirement of the space shuttle program due to safety reasons.