Graduating from director to mogul isn't always merely a matter of thirst for power and unbridled ambition -- "I wish to become the all-powerful Oz of my own entertainment empire!" There are a number of reasons I can think of off the top of my head why a director would take the step.
Life is short, and movie ideas are many. Even the simplest movie usually takes at least a year out of a director's life, especially a writer-director. There's writing the script, pre-production, production, post, and finally release. Many movies take much more time. I reckon Jackson must have spent a good six or seven years solid on three LotR movies, and another one or two in various stages of development. Even the industry's most successful contemporary director, Spielberg, who succeeded very young and has enjoyed carte blanche for most of his career, has only directed about twenty-six features in nearly forty years in the business. He has produced three times that or more. Taking on the Executive Producer mantle allows a director to help bring projects to the screen that he doesn't have the time to direct personally.
As an EP, you get to collaborate with talented people -- and help raise up new talents that you admire.
Also, there's something to be said for building a "brand" for yourself and increasing your worth to the studios. With very, very few exceptions, directors never have enough power. Most spend their careers trying to get their next project going, then fending off studio/financier meddlers when they do get the chance to work.
I can't see a real reason to fault Jackson. To the extent that he has become a mini-mogul, it seems to me that it's out of a desire to help bring movies that he wants to see into existence and to gain greater creative independence for himself rather than just some blind appetite for power.
Regarding his willingness to turn over the reins of TH to another director -- I'm really not that surprised. If he really wanted to direct TH, he would have found a way to settle the New Line lawsuit years ago, or in any case he would have cleared his schedule as soon as the suit was settled. Maybe spending six or seven years around the clock in Middle-earth was enough for one lifetime. I know! Heresy!
Regarding Del Toro -- I have to say that I'm intrigued. Although he does seem to have more of a taste for the grotesque, as that article mentioned, I have no doubt that -- whatever comments have been attributed to him -- he has a genuine affection for
The Hobbit at least. He's not gonna move to New Zealand and spend four years of his life making these movies just to collect a paycheck. When you're someone like Del Toro, who is certainly A-list right now, you don't make that kind of commitment unless you're seriously jazzed about the project. You don't have to.
I'm also surprised that this whole "bridge movie" thing is turning out to be a reality. I thought for sure that that would turn out to be some MGM suit spreading ill-informed rumors (IIRC, it was an MGM exec that broke that news). I made the wrong call on that one.
I'm skeptical about what they'll come up with, but the more I think about it, the more interested I am. This will be, essentially, the first professionally-mounted Tolkien fanfic. Such a film will have a lot less baggage hanging around its neck.