They didn't. Just because one group of observers didn't find the trick doesn't mean there was no trick.
Fair point, but at what level of evidence would you personally say there was no trick?
I'd want a combination of video evidence along with a complete record of the EKG readings interpreted by a team of cardiac electrophysiologists.
Way more than "I don't think they disconnected the EKG because I bet we would have seen some electrical noise." The authors wanted to be fooled, else they had no article.
A quick google suggests you can survive longer than 8 days without water, if you're not moving or eating.
But you'd be in pretty bad shape after that.
Seems like he was in bad shape according to the article.