Re: Amazing that somehow only Samsung was affected
1. So these two suppliers never made batteries for Samsung, or anyone else before?
Well given that one of them is another division of Samsung, it seems quite likely they did make batteries for Samsung devices previously.
2. If they did, then why no major problems with other models, or brands?
Because this device demanded higher battery capacity in a smaller space than any previous device
3. If the two battery makers are brand new manufacturers then why wasn't rigorous Quality Assurance/Quality Control inspections performed including periodic design compliance and random test-until-failure checks performed as part of the manufacturing production process?
Firstly they aren't brand new manufacturers, secondly from the available information the known percentage failure rate is sufficiently small as to easily pass any quality control procedures without detection.
4. What exactly was so radically different with the N-ferno 7 vs the standard Galaxy S7?
A lot? They're entirely different beasts really, in terms of dimensions and power draw not to mention the fact that they, and this is key, don't use the same battery. That's about as useful a question as what was so radically different with the Note 7 vs an Xperia Z or HTC 10.
5. Speaking of S7, who made the batteries for S7 and other Samsung models?
What's that got to do with it? It's not the same battery. It's a fault with a specific battery model design not all batteries from a particular manufacturer.
5. Considering that N-ferno 7 incorporated the ubiquitous—but possibly dangerous—lithium batteries then why wasn't safety a top priority at Samsung for a brand new FLAGSHIP model... including its apparently BRAND NEW DESIGN batteries?
As I've pointed out previously, from the known data the failure rate is so small as to easily escape detection until exposure to mass market. Unless you're suggesting that internal testing prior to release should consist of at least several hundred thousand devices used for weeks?