Genly and Estraven

Genly is an envoy, I would think that he should know about these people inside out. He is the only one who has to deal with negotiations and stuff ( apart from the other people on the mothership, since they aren't doing much) so I would think that he is very good at diplomacy and persuasion. Why does Genly seem so naive to me? He never realizes anything is going down until half way through, like when he was having lunch with people from Orgoreyn, he didn't realize they were mocking him, trying to prove he was a hoax until half way through lunch. He should have always assumed that these people are onto him, assumed that they are hostile against him because he came from the unknown. Genly does not suspect anything beforehand, which is what happened with Estraven, he didn't suspect Estraven until Estraven betrayed him. Seems to me Genly is a happy-go-lucky kind of guy, or maybe he just hasn't received much training for the job. Maybe the Eukumen really does not care about having such an underdeveloped world in the alliance because they would only be a burden, that's why they only sent one person. Also, when Genly was talking about the other Envoys to other worlds, way back in the first few chapters, how they were captured or killed, but then he said there were investigators coming to Gethen before he came, so what happened to the investigators on those other worlds? Were there none? or were they killed or captured too?