I don't get the hysteria about this. Maybe Webb is really struggling right now with some physical malaise. Maybe he was super tired from training and just "bonked," or maybe he just wanted a brisk 1500m "tempo" run to tap off a day of training. Yes, some of these explanations are still a bit bizarre, but they all happen.
It is a bit troubling to note that he ran slow during the indoor season as well, indicating a certain trend. Troubling IF you put your hopes in some sort of heroic resurgence to world-beating form for Webb. It seems unlikely that Webb will break into world-beating form any time soon, if ever again. Watch with bemusement and see what the guy does but attach your emotions to his fortune at your own peril.