Unfortunately, Canada has yet to adopt modern flight/duty time rules as contemplated in ICAO SARPs.
Updated Canadian fatigue management rules were proposed in 2014 (same time FAR 117 went into effect) but their implementation was postponed following a huge industry backlash. Updated draft rules were finally published just a few weeks ago in the federal register (Canadian Gazette) but the draft rules will not become law until late next year, at the earliest.
So due to severe incompetence of the crew they decided not to secure the CVR in direct contradiction to Canadian law.
Securing the CVR/FDR after a reportable event is a shared responsibility -- not just the responsibility of the cockpit crew.
E.g., after being informed by the crew, it's also the responsibility of Air Canada management to ensure that any evidence is secured.
And, at the FAA and/or NTSB -- after being informed of the incident possibly by various parties -- it is the responsibility of the duty investigator to immediately work with the operator (including the operator's maintenance personnel) to again ensure that all evidence are immediately secured.
On most modern aircraft the CVR automatically stops recording shortly after engine stop, and I believe this aircraft sat on the ground for an extended period before its next flight. If the CVR was not secured, then there's plenty of blame to go around.
But we don't actually know at this point if the CVR recording has been lost. Plus there have been incidents where the crew / maintenance did pull the CBs but the CVR recording wasn't accessible anyway due to technical failures.