What Went Wrong With the TAM Trial?

The TAM trial results will be available in the New England Journal of Medicine. In comatose adults resuscitated after out of hospital cardiac arrest, targeted mild hypercapnia did not improve neurological outcomes at six months compared to targeted normal capnia. So something went wrong. And what went wrong? I think there's three options. Either this was a chance, so a type two error that actually is in effect, but they were not able to detect it. Or there was some issue with the trial that could be biased. Perhaps there was an effect, but it was not able to detection it.