So did the other clubs with average championship players like Baines, Cahill, Lescott (even though he was a Championship POTY when we got him I think?) and so on.
You can predict and analyse what's in front of you - at the time when we sold him to Wigan he was worth about 4m and was good in the Championship, he remained there for a reason, not like Wigan were backing off a million suitors.
He was decent for Fulham when he first went in, but wasn't exactly setting the world alight, and was fantastic last season, believe it or not in the Championship again. This year is his first 'leap' in development I'd say, and it's been about 4 years since we moved him on - players mature quite a lot in 4 years.
I'd say it was daft but because we had no real backups, not because of the money for which he was sold.