The surprise is that it is an exceedingly difficult thing to predict. You wouldn't think so, but it is.
I was an EMT for eight years, my wife for 15, and we've had ample opportunity to observe this problem up close, so to speak. I've even chatted up doc's about it, because I was skeptical, too (that was when I was learning that pre-hospital cardiac arrest survival rates are below 2%, no matter what you see on TV). It turns out that the best radiological techniques, even going to the cath lab (angiography) which is the best diagnostic of all, might tell you that there is some atherosclerosis, but doesn't predict heart attacks very well unless the atherosclerosis is so severe that they immediately place a stent during the cath, or schedule bypass surgery immediately.
Consider, for example, someone who goes in to the doc for chest pain. Diagnosed as not a heart attack, but out of an abundance of caution they get a stress echo, EKG, etc. and pass all the tests. They might even have acceptable cholesterol levels. Then, bam, a week later that same someone kicks the bucket. Seen it/heard it many times. Such a person could even have an invasive diagnostic like a cardiac catheterization done on a Monday. Then, diagnosed with atherosclerosis but not to the extent that a bypass or stent is required, the doc puts them on statins on Tuesday, and they are dead of a heart attack on Wednesday. They throw a clot, or an artery spasms, or something just spontaneously clogs. It happens all the time. Worse still is the person who is otherwise super healthy. Great shape, beautiful EKG, nothing heard, noticed or felt on exam. Low cholesterol. No reason for an expensive CT and like hell are they going to send you to the cath lab. No reason to suspect there's a time bomb. It's also possible that the heart attack was electrical in nature. Your EKG could be totally normal on a Monday and something goes sideways with your heart's electrical system on Tuesday. There's just no way to predict something like that.
You need to hope that when and if your time comes to stare down the barrel of the cardiovascular disease gun you get some obvious but non-fatal warning signs and symptoms. Certainly that happens a fair bit as well, but not nearly as often as you might think, and many times those signs and symptoms are ignored because denial is part of the disease process.