Last year on the very same course Bekele ran 28:14, Tadesse ran 28:24, and Ritz ran 29:02. So, Bekele ran 32 seconds faster than last year, Tadesse ran 41 seconds faster, and Ritz ran 68 seconds faster. Of course, given different course conditions, it's near impossible to compare one year to the next, however, if this year was not fast, as you say, last year must have been a bit slow.
Last year was run in a mud pit, and described as having gale winds. That's why it was so slow. Last year bek took off with 2.5 laps left after tadesse tried to make a move. this year he waited a lot longer. He jogged most of this years race and took off at the end. (as did almost everyone else).
Or perhaps it was this basketball shorts that he ran in last year that gave him such a big win!