Well, "A Serious Man" didn't receive any Oscars. Ironically, there wasn't much of a "Jewish" feel to the winning movies this year. I'm reading You Should See Yourself: Jewish Identity in Postmodern Culture (2006), a collection of essays, and in one on film, there is this quote by Malma Sarah Saval, from 2004: "'Over the past several decades there has been a shocking dearth of Jewish films in the mainstream Hollywood market. Perhaps the most noticeable absence in recent years occurred during the 1990s, in which period not one American movie featured a rabbi. On the flip side, an everlasting stream of movies keeps us in constant supply of Christian clergyman.'"
Rabbis, and what they represent, play a prominent role in "A Serious Man". Could "A Serious Man", consequently, be "too Jewish" for mainstream American culture, "too Jewish," for the Oscars? (I remember a 1996 exhibit entitled "too Jewish?" at the Jewish Museum in NY).
I suggest that "A Serious Man" makes audiences, Jewish and non-Jewish, uncomfortable, which is the Coen Brother's trademark (to disturb, to provoke), too uncomfortable for the Academy. Rather than "flattening the difference" between Jews and non-Jews, as Hollywood films featuring Jewish characters do, making Jews palatble for mass audiences by making them seem not so Jewish, not so different, "A Serious Man" calls attention to the differences between Jew and non-Jew, i.e., between a Jew and his Gentile next-door neighbor, who has his son miss a day of school to hunt deer (something a Jew would never do).