The other thing that got me very curious is how did a monk develop heart disease. I mean he must have been very very active and probably eating healthy.
From the article it appears that he was hardly sleeping in order to keep up with responding to people. It also makes it clear that other people's anxiety was passing on to him. Chronic exhaustion and stress might be OK for a young man if it's part of an effort to break his mind/enlighten him. But long term it's not surprising that it would seriously affect someone's health.
As the article mentions, Buddhist monks in East Asia these days mostly don't follow the ascetic lifestyle of days past. They smoke, drink, eat meat. Some of them may even marry.
The other thing that got me very curious is how did a monk develop heart disease.
Age and genetics. One will suffice, if not both.
Plenty of people develop heart problems who eat well and keep active. Healthy living improves your odds considerably, but doesn't put you at zero risk.