I think he really did truly understand the jew, but he just thought that he could subsequently manage them. In the Nation and Race chapter (I think it is) of Mein Kampf, Adolf writes an alphabetical step-by-step path on the mutation of the jewish virus, all the way from the beginning up until complete overt judeo-bolshevik control. So I don't think he was ignorant of the problem, I just think that knowing all that he did, he felt that he could deal with them accordingly. He was wrong on this count.