What does "the general concept" of an abstract noun mean in a specific case?

Some abstract nouns can be both countable and uncountable.

A common explanation to distinguish them I have come across is

Countable when you refer to a specific instance or occurrence.

Uncountable when you say the general phenomenon or concept

And I found this example.

The first and only flight of the J8M1 prototype took place on July 7, 1945, ending in a crash due to engine failure.

The "engine failure" here is used without an article, so it must refer to the general concept.

But the sentence states one individual accident caused by an engine problem, so isn't the engine failure already a specific occurrence?

If it's correct, then I don't get why this is treated as a general concept.

_{NOTE: Since this answer was written, the OP has edited the original question to include most of what I wrote, and then asked a new question about my answer. I am leaving my original answer intact and appending it to cover both.}

Original answer

A singular noun can often be used in these two ways:

• Countable use, where the noun refers to one particular instance, item, occurrence etc. This normally requires the indefinite article.

• Uncountable use, where the noun is used without an article to refer to a general concept.

So:

"...due to an engine failure" uses it countably, to refer to a specific instance of engine failure.

"...due to engine failure" uses it uncountably, to refer to engine failure in general as the reason.

Another comparable example is "due to an illness" and "due to illness", where the former is a specific case of illness and the latter is illness in general.

Appended answer

"Engine failure" can be considered a general concept because it is something that happens, or can happen. Childbirth is also something that happens - you can speak about it in general and say things like "childbirth is beautiful" or "childbirth is painful", without an article or determiner, because you are not referring to a specific instance. Same goes for "engine failure", my original example of "illness", as well as countless other concepts.

Concepts/abstract nouns don't need articles because you can't count them. They only acquire an article when you refer to a specific instance of something - for example, death is an abstract concept, but you can speak of "a death" or "the death of [a particular person]".