OKC got lucky that the balls bounced the way they did. There's no reason that had to get the #2, #4, and #3 picks (Durant, Harden, Westbrook) in those draft classes. They just have easily could have been #5, #6, and #4 (Jeff Green, Galinari, and Tyreke Evans).
And those weren't even the worst case scenarios: guys like Hasheem Thabeet and Jonny Flynn were picked around OKC's big 3.
Luck had nothing to do with it? I would say that is not true.