Can sudden cardiac death from something like vfib happen to a healthy person and if so why? anyway to prevent or detect it ahead if time?

Yes: Yes, sudden cardiac death can happen among healthy, active people. Certain conditions may cause it like anomaly in coronary artery or other genetic abnormality, or cardiomyopathy. Some conditions maybe suspected by a physician based on history, exam, EKG and echo of a patient. If a patient is identified to be at risk of sudden death an implantable defibrillator could save a life.