Few reasons for this...
Poor Captain's picks. I think it must be harder for a contemporary of Phil to leave him off the team than it would have been for someone who is removed from the Tour.
Course set up. This ties into to the point above. Everyone knew what it would be like. It wasn't a secret. Yet Furyk picked Phil, who is pretty much the worst driver on tour.
Poor strategy. To compound the two above points, Furyk then sent Phil out in foursomes. Foursomes? Phil? On that course? No, just no. That was always going to be a disaster.
Lack of preparation. Only Thomas came over for the French Open, so he knew what to expect. Also, the lack of preparation due to the Tour Championship, which meant loads of the US players had zero adjustment time, few practice rounds, jet lag issues. I know that a lot of the Euro players were also at East Lake, but it is always easier coming back home, plus they were really fired up to win due to...
Arrogance. "The Greatest Team Ever". Sorry, that was just wrong. You can start talking about great teams once they have won and dominated. There was a common school of thought that while the US team was great on the PGA Tour courses, they would struggle on this set up. I can imagine this got the back up of a lot of the European players - due in no small part to Alan Shipnuck, as referenced by Rory and Poulter post event. Never poke the underdog bear..
It's the captain's prerogative to set up the course as they see fit. Two years ago there was light rough, lightning fast greens and it played like an "easy" typical tour venue which favoured the US team. No problem with that. I am sure whoever is captain in two years will do the same at Whistling Straits and good for them. It will be up to the European team to adapt - and maybe the captain will pick long but inaccurate hitters to mitigate some of this course advantage.
You can't manufacture chemistry. Creating these pods of 4 players sounds like a good idea until the players within the pods play poorly, and then you are stuck because you don't want to choose partners from outside the pods. This ties into egos (hello Patrick Reed, nice 85 on Saturday morning!) and the Europeans do have a sense of cameraderie, maybe aren't as corporate, and are willing to poke fun at each other and play with whoever the captain thinks is best suited. Rather than 3 pods of 4, there is one team of 12, all working towards the same goal.
I was surprised that it was as lopsided as it was ,but I was not surprised at the result. The top European players were always more likely to find fairways, and on this course it was imperative. It was like a 2000s era US Open set up, and the likes of Stenson, Molinari, Fleetwood and Rose all shine on the skills that demands.