If the Chinook WAS totally serviceable
It wasn't. The BoI report includes a distressingly long list of problems, including both faults and defects.
As ever it is the information the BoI didn't read, or weren't given, that reveals even more. Minor things like "positively dangerous" and not recommended for Service flying. We'll just have to wait and see if Lord Philip asks ACAS why he ignored these facts. After all, the regulations required him to record his reasoning.