I think Monaco must be a super fast track. If we take Nick Willis, then I'd have bet my house on him not being in 3:30 shape.
He ran the Mile in London less than a week earlier, had drafting to the bell and even 440s of 56.2, 1:53.6 & 2:51.1, very similar to the pace he had in Monaco (a tad slower in London to 1200m), yet he was only able to manage a last lap of 61 in London. In Monaco his last 400 was about 54.2 and his last 300m was about 40.2. Can someone really improve by that much in less than a week?
Surely the difference between the 2 performances was that his endurance was not good enough in London, and I'd have thought all the endurance work should have been done by now. Can someone improve that much with 5-6 days of speed work?
And no, I am not suggesting anything sinister or PED use, I just think that there must be something special about the track or conditions in Monaco. I think I remember Gregson & the big American (name has gone for a sec) running 3:30 there last year or the year before. That came as a shock to me then, as I didn't think either of them looked like 3:30 runners, and neither athlete has done anything approaching those times since.