That is all true, but regardless of his misdemeanour any legal pilot could/would have succumbed to CO incapacitation.
What I don't perceive in all the concentration commenting and dealing with one man's crime is anything directed at maintenance. Either via the written procedures which may not call for CO leak inspection, or perhaps the organisation responsible for maintenance which at best failed to see incipient exhaust leaks.
No leaks and we'd not have heard of the ancillary crime !