Well I think there is a slight difference between pro-racing in 1997 and 2013!!! As Horner said, in the weeks leading up to that Basque Country, he was sick and injured and struggling with living in Europe so his morale was rock bottom as his training was poor. He was then flung into De Panne, Flanders and Basque Country started the following day. It wouldn't exactly be surprising he fell apart as that schedule would be completely alien to a US domestic pro, never mind one struggling with the culture in Europe.
See that's the thing, when Horner decided to return to the big league's, he swore he would never live in Europe and as far as I know he doesn't and is in the US at every opportunity, I think he took the attitude that he would do things on his terms when he returned to Europe.
BTW, I think its unbelievable what Horner is still doing at his age so no way am I defending the guy.