The original announcement had two key words.
'Traditional', as others have said, was largely misinterpreted. They wanted swords and magic, and a place for all the standard D1D tropes, but that's about it. Some people found this too confining when they really shouldn't. One of the top three was loosely based on Renaissance venice, if I recall correctly.
The other key word was 'scope'. The submission should have a scope similar to the Forgotten Realms. That was the tough one--they wanted a campaign setting with many countries, societies, cultures, and continents that could provide ample room for a wide variety of players.
I quickly realized that my current homebrews couldn't cut it--they were too mishmashed, peurile, or derivative of famous literary works. The challenge was to come up with something original, out of whole cloth, and pitch it to the committee. So I spent a week or so thinking and came up with two very original ideas that I liked.
I stumbled over each of these. My first submission fell into the 'Golden Age' theme that seemed to hit a chord with the selection committee (as evidenced by three of the top eleven settings having that direction), but I wanted to give it a touch of Arabian Knights feel in that magic was something gained by bargaining with Powers, not the usual cost-free spellcasting. I emphasized that in the one-pager, and I realize now that it probably didn't go over well. I also described the setting in terms of its major city, which doesn't speak well for scope. I still hope to make this a homebrew or a source of short stories.
My second setting was even less traditional, having the various races dispersed to the moons of a ravaged world. More scope, more than one world? No--because the exodus had unified their cultures considerably. In the end I realize that this one had even less scope than the other--but the seeds planted there have grown into a novel that I am currently working on.
I have no doubt that whoever read the submissions, if they weren't too tired to read mine, thought "huh-cool!". They were cool ideas. But it's obvious to me after seeing Eberron that they both failed the 'scope' test horribly.
Small ideas are easier to conceive and easier to advertise than big ideas. What really, really impressed me about Eberron is that it is just brimming over with original ideas and storylines. The monster nation of Droamm--how cool is that? Very cool, and a world where that was the only unique thing would be worthy of a homebrew campaign and a colorful, entertaining one-page setting submission. But wait--there's the Silver Flame, the orcish druids repelling the invasion of the Daelkyr, the threat of psionic Sarlonan overlords, the dragonmarked houses, the Lords of Dust and the legend of the primordial dragons, the Last War...the list goes on and on. I just started running an Eberron campaign, and it is a DM's paradise! Eberron has scope, lots and lots of scope, and that's where both of my submissions fell short.
Of course, Keith didn't put all that into his one-pager, and he had help from the other designers after he won the setting search. Keith had a healthy dose of luck on his side that his one-pager was read by the right people and percolated to the top of the heap so that he could show WotC a little more of his world in the 10-pager. His one-pager doesn't go into all those details; if I remember correctly, it talks a bit about the Last War and the Dragonmarked houses, but really emphasized above all the pulp/noir feel that he wanted to convey.
I think it's availiable on his website if you want to read it.
Anyway, that's my persepctive. It was fun to write the one-pagers, and I'm getting some good use out of those ideas. I don't begrudge the finalists or winners one bit, as what I've seen of their work has been top-notch. The setting search was a fun ride!
Ben