I agree with earlier comments. I’m new to book proposal land, but I’ve pitched (and had pitched to me) many movies and TV shows. I’d put the premise right up front. “What if the nazis won the war?”
Also, that third paragraph, if you’re going to go with background, should tout how much research you’ve done, rather than give the impression of a sort of light-interest-wouldn’t-it-be-jolly-to-write-about-this kind of thing. What about turning the negatives about what’s wrong with the literature today into gusto about strong Jewish characters. Just in case this publisher has a few books on the market in this area, or loves this genre (which is YOUR kind of editor, no?).
Go get ’em, slugger!