Frankly I don't think Rupp will ever make a mark where it counts, in world class competition. He doesn't have that depth, as others have noted. For example, the last 10K he ran prior to World Champs, was all about testing his speed in the last 600, which was quite good, except it was after rolling 70 second quarters. BFD when the Ethiopians and Kenyans can bust out the low 50 quarters after running regular 65s.
But more than that, there is something more imprecise and unscientific. He just doesn't seem to me to have that killer focus, that (excuse the awful, awful cliche) "eye of the tiger." At the start of the 10K, he looked like a scared, wide eyed little boy, not a runner capable of scoring a medal against world class competition. I've watched him race before, and every time when he's not running away for an easy win, when it's actually HARD and he's got COMPETITION, I can see in his eyes the moment when he just switches off, and is content to settle for a top 10 and a PR.
He's a product of a growing mentality that emphasizes personal bests and easy wins like top tens and winning the age group. That kind of mindset should not be acceptable.
I also think the money thing is a huge psychological factor. The Kenyans and Ethiopians are running for their VERY LIVES, and the LIVES of their FAMILY. A win means money to care for everyone for life. That is a huge mental edge, an incentive hard to transcend by our soft athletes with their Alter-Gs, altitude houses and 200K shoe contracts. They have nothing at stake.
The reason we were better back in the 60s and 70s was because those runners were, in a way, like the Ethiopians. Working class kids coming from no money, for whom running was not a career so much as a means to achieve financial security. If you won Gold, then that meant you could get a good job...but until then you had to scrape by. Hell Jim Ryun bagged groceries to pay to travel for altitude training before Mexico City. Prefontaine lived on food stamps. Shorter was enough of a realist that he got a law degree, because at the time there wasn't much of a future as a runner.
I'm not saying we should go back to the days when pro runners had to live in poverty, but I do believe the desire to escape that state of live was a incentive when it came time to racing.
Now, when our top athletes are bought a paid for by Nike, when they have that soft cushion to land on, and they can generally win races in the U.S. (yet are virtually meaningless in the world scheme), what have they at stake by not winning, not getting a medal in a world class event?