So it was the engine rather than the aircraft. Faulty design? Faulty materials? Faulty assembly? Faulty maintenance? Or was a combination of two or more of these things?
Inspection intervals are set by known knowns - knowing in advance the failure rates.
Manufacturer has to be relentless in testing and gathering data to seek failure trends before they happen - that can get expensive. Of course, not as expensive as some lawsuits....
(I have had engines fail spectacularly during test - sick sound, sicker feeling).
Very likely a combination. Nobody checked and noticed stress fatigue and NDT probably hadn’t run any scheduled tests as they cost too much.
As much as Tort lawyers want a jury to believe, NOTHING is perfect.
Accidents DO happen.
There is a Cost vs Benefit comparison for everything. However, paper shufflers, i.e. Lawyers, Politicians, Admin, HP, “Journalists” seldom get hit with their own “accident “ investigations. When they do, they get one of their own to deflect the accountability.
For physical, engineered & manufactured products you work as hard as you can to make the product safe & durable. You set scheduled inspections, if any, to hopefully insure safety without unduly affecting the use of the product.
Still, “some days you get the bear, some days the bear gets you.”
Yes, no doubt.
Generally when there are “serious issues” in aviation it is a result of multiple events. We’ve been at this long enough to have culled out most of the obvious stuff. Now what bites us is when multiple things happen in just the right (wrong) sequence. It may turn out to be a manufacturing tolerance that is just a bit too loose, a blade at the limit, a merely cursory inspection, some significant in flight event previously... Stack them up together and you get the flight crew having an opportunity to show off their skills and training in a real world incident.