Firmware -- undebuggable, unobservable, unfixable software, jammed into your devices -- is the enemy.
A component failing? Electrical components fail. Sometimes it's a manufacturing defect, sometimes a design defect, sometimes something under or over-volted and it was enough to cause damage to any given component.
Could be an IC, could be a capacitor, could be a poorly laid trace. A poorly shielded RF source could even damage any number of components.
I mean, in theory a single high charge particle from that rare cosmic ray that reaches the surface of earth running full-steam-ahead through an IC could cause just the right amount of damage to make it fail although this would be an incredibly improbable scenario.
Same goes for HDDs, televisions, your clock radio, whatever.
SSD has a problem in that almost every failure case looks more like a head-scratch than a bad sector.
Even the most local problem that is excessive writing on a sector can take the entire chip down.
That wire is the one delivering power. Point being, while things are so complicated that you often can have a lot going on and still try things, there are still single points of failure that can never be fully covered.
Because they don't die incrementally. Wtih a hard disk you'll get bad sectors, growing slowly over time. Or a head crash and then it's all dead.
What could cause an entire SSD to die at once? I would totally understand bad sectors, but the whole thing at once? Where it doesn't even try to read existing data?