Science fiction novels about post-apocalypse survival are easy to write. All the big stuff usually takes place before the novel starts, and it doesn’t have to be explained. Sometimes, as in The Road, you don’t even know what happened. All the complications of civilized life are pretty much wiped out, and all the characters have to worry about is survival. Life and death. Maybe moral scruples come in there somewhere, but it’s mostly about scratching a living from what’s left, kill or be killed, and nothing to look forward to but more of the same.
Most dystopian novels aren’t much more complex. The bad stuff is already in place and it’s the duty of the characters to endure. Maybe there’s room for some heroism, which will probably lead to being demised by the bad guys (usually an all-controlling government, usually hand in glove with evil corporations, usually with at least one, preferably two, truly evil power mongers). Again, it’s all about survival for the masses, with some rebellion by brave but hopeless losers thrown in to raise hopes.
There aren’t too many novels that ask how things got to this pass. Even fewer that try to show how it happened. Because that’s difficult. You have to deal with reality, which operates slowly, which hides its most important details in plain sight where they can be ignored in favor of entertainment that keeps the populations nicely sedated and distracted from what’s going on.
Come to think of it, maybe that why we have mostly the kind of novels I described in the first two paragraphs. The writers, being just as oblivious as everyone else, don’t know how it all happened, so they really have no option except to wave the writerly equivalent of a magic wand. Hocus pocus, it’s now 2063 or 2258 and everything has already happened. Earth groans under the domination of (fill in the blanks), the few survivors are eating each other for breakfast, are killing zombies, or have fled earth to live on (fill in the blanks).