Geoffrey Mutai did not have what Geb had. Perhaps only one other man on the planet did.
As for Tergat, please understand that he ran 26:27 at age 28 and 2:04:55 at age 34. He was not the same guy. Tergat ran 2:04:55 when he could probably only run about 26:50.
Paul Tergat could have run 2:03:30 in his absolute prime. Perhaps Mutai could, too, but as I've illustrated, Mutai will not match Tergat on the track as he's taken a different path.