The first hour of treatment after a heart attack is critical. Such treatment requires a variety of drugs which wouldn't have been available on the flight. That's why a diversion would probably be advisable. I am in no way attempting to be judgmental of the decision making process both in the aircraft & on the ground.
Obviously I wasn't there & was only reporting what I read. My wife however, works in a major cardiac unit & is horrified by this case.
PS Whilst it's true that in any heart attack there is damage to the heart muscle, the longer that the patient has to wait for specialist treatment, the greater the damage.