Sounds like he had an arrhythmia, and might have been resuscitated if there was a defibrillator / AED available. In the article his friends said they tried to revive him until the EMTs arrived, but unless they were trained in ACLS, and depending on how long it took the EMTs to get there, it would be very difficult. Of course, it could have been something else, like a pulmonary embolus.
That's what happened to me when I dropped dead on the basketball court in November of 2018. But the guys started CPR and first aid was there in about four minutes (they tell me) with a defib. I awoke in the hospital several days later.
Every day above ground is a blessing.
The problem was it was a folk festival. If it had been a rock show they could have turned on his amp and tossed a glass of water on him and that might have jumpstarted the old ticker.