I think that the only explanation for Geb's "failure" is the that he did not time his training properly to be in the best fitness on April 23. Look, he was running 58 minutes for a half marathon in JANUARY, and then 1:11 for 25km six weeks ago.
Even when he was running his world records on the track they were never more than a couple of months apart. He was asking his body to remain at the highest level possible for 3 MONTHS.
Look at the Tergat/Korir 2:04's: Both those guys did not have any significant races in the 2-3 months leading up to that.
Geb just shot his wad too early in the season. I think that he will be back in September or October and give it another shot at Chicago, Berlin or Amsterdam, albeit with no other world record attempts.