Denny O'Neil, who was the Batman group editor at the time of Knightfall, has said a number of times that plans for the event were well under way before the "Death of Superman" story happened. It's fairly easy to confirm this, if you consider the introduction of Azrael to be the first part of a long story, and you believe that his introduction was always meant to be the start of Knightfall. But even if Knightfall had been created without influence from the Superman offices, it was part of the collective superhero hive mind that would see variations on a theme get more and more ridiculous.
Knightfall was the next step.
To O'Neil's credit, what makes Knightfall work is all the set up. Jean-Paul Valley is introduced a year earlier. He becomes Azrael. He quits being Azrael. He gets trained by Batman. He's in the background as the battle against Bane unfolds.
In fact, the main story heading into the show down with Bane has nothing to do with Azrael, it has to do with the fact that Batman is starting to lose it. He is working himself too hard. The physical damage he does to himself night after night is nothing compared to the mental damage. Robin is worried. Alfred is worried. The audience is worried. Batman is burned out, but he keeps working.
And that's an important point. It establishes that Bruce is perhaps not at his best when Bane gets a hold of him. It also supports his initial decision to give up, to hand the cape and cowl to Jean-Paul Valley. Batman never loses and he never gives up, but he does both in Knightfall, so the creative teams had to make sure he was in a place where that would happen.
Bane is almost secondary. Were he anyone else, Batman would have chosen to go on hiatus. Bane basically forces him to.
What's interesting is that what leads Batman to this point does not, at least initially, have anything to do with Bane. He first starts showing the wear and tear of the job while trying to stop Black Mask; Batman gets beaten down by Black Mask's bodyguard, a character we've never seen before. This would become a theme.
While still physically spent from stopping (yet not capturing) Black Mask, Batman faces off against a new character named Metalhead who is, frankly, a pretty awful creation. But Metalhead also gives Batman a good beating, although Batman eventually wins out. But these back to back beatings are enough to wear Batman down and the physical abuse begins to weaken him mentally and emotionally as well.
Given Batman's history of putting up with a lot of abuse, it's hard to believe that these battles in particular would be wearing him down, but we have to take them with a grain of salt, just like we have to look past the fact that for some reason he's decided to shut himself off from everyone around him. One of the key factors in Batman's downfall is that he doesn't let Robin (Tim Drake) help him. He continually relegates Robin to back-up.
The problem is that by the time we get to Knightfall, Tim Drake has become a fairly proficient vigilante in his own right, and Batman knows it. In the publishing world, Tim had been Robin for a few years at this point and had even had three separate series. His abilities at this point should have been unquestioned.
To make Batman's cold shoulder somehow more believable, Tim is regularly written out of character. It doesn't seem like writer Doug Moench ever has a grip on who Tim is and more often than not this Robin comes across as the last Robin, Jason Todd. Moench writes the bulk of the first few issues, but thankfully Chuck Dixon eventually takes over, and say what you want about Dixon, but he understood who Tim Drake was from the start.
It's not just Tim Drake that's an issue, though. By this point in his history, Batman has a family. Knightfall is a story that would have worked much better before there were so many branches of the Bat family tree. The idea that Bruce would hand over his mantle to Jean Paul, let alone that he'd be allowed to be Batman, is a stretch, and this is coming from a guy who LOVES No Man's Land.
Knightfall is overly long and logically inconsistent, but still kind of enjoyable. What's interesting is that, like the Death of Superman before it and the Clone Saga after it, the ultimate point of Knightfall is that 90s style superheroes don't work. It is refuting what is going on in mainstream superhero comics while also indulging in it. That's an impressive line to walk.
Still, the event has problem that it's predecessor (The Death of Superman) didn't. It was overly long, it involved many titles that didn't normally interact, and there weren't consistent creators.
The art, in particular, is uneven across the event. The main Batman books are more or less stable, but bringing in other books, some of which had very different aesthetics, was jarring (I'm look at you, Catwoman).
Just like the Death of Superman and the Clone Saga, Knightfall seems designed to show us why the original is better than the knockoff(s). In this case, I don't think Knightfall fully succeeds, in part because Azrael is set up to fail, but also because Batman operates in a grey area. The idea that a more violent version of Batman would somehow be the antithesis of the usual Batman is flimsy. The line for Batman is constantly moving.
There's also nothing about Bruce Wayne, in particular, that makes him the only person who can be Batman. Jean Paul Valley is a bad example because, again, he was created to go off the deep end. But the final arc of Knightfall involves Dick Grayson stepping in as Batman, a role he could pull off just as easily as Bruce (and does, when Bruce "dies" in Grant Morrison's brilliant run on the Batman books). In many ways, Dick is more qualified that Bruce because he's more emotionally stable. Even with all the sidekicks and partners, Bruce still has a martyr complex, while Dick is a team player.
This isn't how it plays out, of course, during Knightfall. Just as Tim Drake is pushed aside, Dick Grayson is made to be less than who he really is, all for the sake of showing us that Bruce Wayne is the one true Batman.
He doesn't have to be, of course, which makes Batman different from other iconic heroes. There is only one Superman, one Spider-man, one Wonder Woman. They may be replaced, but their origins are unique, their powers specific to those origins. Batman's origin isn't that unique; even if you decided that, to become Batman, a person HAD to see their parents die in front of them, I'm sure there are a handful of people who could qualify. Expand that search to the entire world and I'm sure that number would get pretty big, pretty fast.
Bruce's abilities were learned. He's not a superhuman. His money has obviously made becoming Batman easier, but Daredevil has done relatively the same thing without it.
All of that is to say that an event built to show why the main character is special doesn't hold up when it has to go to great lengths to make that case, and even then isn't definitive.
At this point, what makes Bruce Wayne unique as Batman is his history. The cape and cowl carries so much baggage at this point that there's really only one person who has the knowledge and experience to pull it off although, again, Dick Grayson could make a reasonable claim. At this point Tim Drake probably could, too.
Knightfall is entertaining, don't get me wrong. It's far too long and the quality is erratic, but there are some solid adventure stories sprinkled throughout. And while I've never cared for Bane, he's clearly become an iconic villain, so in that regard Knightfall was a success.
But as far as 90s events are concerned, Knightfall doesn't hold a candle to the Death of Superman.