WWE had interested in Okada but Okada didn't reciprocate because he and his mentors were VERY skeptical of the WWE's track record with foreign talents, especially Japanese. Or at least that's what I heard.
and if you have a choice between Okada and KENTA... If I were WWE I'd probably go with KENTA. He's further along in English and with his size he was more likely to be accepting of a lesser role whereas there would have been far more backlash for screwing up Okada. Okada is literally Japanese Orton with an incredible work ethic.