I find myself often being irritated at elements in situations that help characters succeed, elements which are also highly unlikely or even illogical. But often, if not more, I find myself angered by things that too inconvenient. Improbably inconvenient. But am I alone on this? Is it a pedantic irritation or is unlikely inconvenience bad writing?
To be very clear: (a Fantasy setting) If characters are fighting a fight they'll never win, and a never before mentioned/foreshadowed/hinted at dragon swoops down and saves the day, that would be too convenient.
Oppositely, if the characters are winning the fight, but that same dragon swoops down and makes them lose, that would be too inconvenient, at least in my opinion.
Now, if I understand correctly, there are multiple components to this: The dragon hasn't been mentioned, for the dragon to appear is very unlikely and the dragon is irrelevant to what is happening (the fight). I believe there is small differences in inconvenience based on which of these three it suffers from. I'll tackle them in order.
In a book I was reviewing, there is this whole species that is enslaved secretly by some bad people. A resistance freed the species, and chose to hold them in airplane hangars, waiting for whatever, not important. The resistance had not planned ahead enough though, and neither had the author. The main character let's us know that "OH NO! You have all the males in one hangar together? If they are left like that, they kill each other!". Have in mind, this was the second last chapter.
So, this is a problem, and it comes out of nowhere, because it is based on never before mentioned information. To me, it comes off as cheap. Imagine someone is attacking the airstrip, and instead of kill each others, when the males are in the same room, they all give each others superpowers, and are therefore conveniently able to repel the attack. There could be a smart and scientific explanation to this, but it wouldn't matter, because if it hadn't been mentioned before, it would be cheap and too convenient.
Then you have inconveniences that are just very unlikely. Imagine our hero is chasing the villain, and he is close to catching him, and then he is struck by lightening. Too inconvenient. Also, this inconvenience suffers from the last one too, it is irrelevant. Unless the villain has superpowers or is a god, it is completely irrelevant to the story and the conflict in question that the lightening would strike our hero. Now, if there's a thunderstorm, these people are on top of a mountain and they have giant metal poles attached to their heads, then sure, it is a little less unlikely. Perhaps even more likely to happen than not. But relevant?
Though I must admit, I am very unsure in this "theory", as I have witnessed inconvenience and liked it, like in Whiplash, where the main character is hit by a car before attending the concert he was supposed to play at. Though, he was speeding, lowering the unlikeliness, car crashes are a widespread phenomenon, so it doesn't require mentioning, but is it irrelevant? From a narrative perspective, perhaps not?
Anyways, one thing is for certain, if convenience suffers from any of the aforementioned things, then it will not fly. But is it tolerable for inconvenience? My core question is really this:
Is there narrative-wise an inherent difference between convenience and inconvenience, making it so that the same rules don't apply to the latter?