Here's my take... And I'll try and be nice about it.
DC most likely was planning on killing New 52 Superman about a year or two before they actually did it, based on interviews I've read about the decision. The writers had to have Nu52 Supes go through a number of things that would cause his death. Being made into a God of Strength in JLA, using Kryptonite to restore his powers so he could fight Vandal Savage, etc.
I like RAB's reasoning but I personally think there is a lot more to it than that. The New 52 Superman simply wasn't working. I constantly read all across the internet (this board as well as a lot of other places) that the fan outcry was (for the most part) against the Nu52 Superman because of how out of character he was constantly being written. Doesn't matter where I went, all I read was how upset fans were at Superman being written so out of character with only a glimpse here and there of the man we all know and love.
In saying that, it's no surprise the Lois and Clark title did so well. The Superman we all knew and loved had finally returned. Reading RAB's reasoning here, it definitely makes sense to me that Lois and Clark was outselling the main Superman books because this was the Superman that most fans wanted, not the one that was almost always acting so out of character. So, DC made the smartest decision they ever did for Suprman in the 5 years since the New 52 started and that was by killing the New 52 Superman and giving us fans what we wanted by giving us the real Superman, his marriage to Lois and a son.
Glad your enjoying the trades, more power to you. But for numerous reasons, I just could not bring myself to like the Nu52 take on Superman because he wasn't the character I know and love.
My main beef with NU 52 was when they jettisoned Lois and his parents from Him, losing his humanity, and having him hook up with WW as ultimate power couple!