Well, I’ll wade into it. My best answer is “Group Think.” Its like asking why Blacks in America consistently vote Democrat when they are being really systematically exterminated by those same people? Its hard to explain but it comes in the form of peer group pressure, the impossibility of having a civil conversation, and the almost unified reliance on MSM and NPR for news. You get lots of people systematically mislead that you just can’t set straight. Does that make any sense?
I live this every day, greeting, loving and being with Liberals who you just can’t tell the truth or you will be hounded and ostracized. I never quite understood this until I started studying Crowdsourcing. And it turns out.. groups are maintained by “conformity police.” The left has infiltrated the Jewish community and the further they from Orthodox the easier it is to get them to buy into the lies that these people are spreading. This is because of guilt. Jews who are at all religious and not orthodox feel a sense of guilt about not keeping to the law. Even when what has been settled by the Rabbi’s of 1400 - 1800 years ago is just non-functional in 2013...
Talmud is a blessing and a curse. The oral law was never to be recorded and then it was. The oral law is the “How-to” implementing code for following the Commandments in Torah. IF this how-to mismatches reality, you get craziness. If you suspend the how-to by refusing any how-to you get what happened to the Karaites who just tried to follow the law as it is written and ended up sitting in the cold and the dark every Saturday among other problems. There is still a community of Jews who hold to this though as they are deeply suspicious of the Rabbis who wrote the Talmud.
Opposite of the Karaites is the Conservative/Reform/Liberal Judaism movements. These movements represent the still religious (non-secular) Jewish community and they rejected Talmud almost whole cloth in the 1800’s and the Conservative and Reform movements have slowly been walking back.
You have to put this in context. In the early 1800’s a theory called Higher Criticism was formed that showed pretty definitively that 4 distinct sources could be teased out of the text of the first 5 books of the Bible (Torah). This was kind of meant to hurt the Jewish community and it destroyed it in many ways.. but it has come to bite the Christian community just as hard. This co-incided with the age of the “Enlightenment” where “Scientism” started replacing faith in God as the ultimate source of truth and value for the elite and the educated.
We saw the rise of Spinoza’s rejection of God and the variations of Atheism and the rise of “faux” Judaism in the form of Communism. Communism replaces God with Mankind as a community and substitutes the achievement of a perfect society of the “proletariat” for the Messianic age. Much of philosophy and science have been bent toward this goal, regardless of whether the people working this call themselves Communists or not. At the front end, these social minded reformers made the lives of the beneficiaries of their programs lives better but just as we see, ultimately, Communism is implemented by tyrants who think they know better than the masses and end up deciding to kill anyone who opposes them and that gets to be one pile of people as their suffering grows. And, in spite of what ever they call this faith, Progressivism, Liberalism, Socialism, Environmentalism it keeps gaining believers and delivering misery for humans.
But, this is the issue with “faux.” or fake. Because the Bible teaches these lessons too, being kind to the stranger, providing for the sick and the needy, making sure they are treated with dignity and the same as any other person. So, certain individuals have attached themselves to the religious community and overlaid the goals of Communism/Socialism with the Biblical messages from Torah and by insisting that God is just a “concept” are able to walk away from the moral clarity of actually believing in God. They instead substitute working for “Social Justice” which isn’t at all what Torah teaches about Justice, and “Tikkun Olam” repairing the word, when they don’t have a clue just exactly what that means except, more social justice which translates into supporting the leader’s schemes to create a socialist utopia.
SO, as a group, Jews in America except for some of the Orthodox are deeply misled and working against their own interests and no one can tell them different. But, doesn’t that describe about 50% of all Americans?????
But Jews seem to have a tradition of just the opposite in just about everything else, with American politics being the anomaly.
There are old jokes from the Jewish comedians along the lines of "Put (pick a number) of Jews in a room and you'll get (more than that number) opinions." And I've heard (what I presume to be true) family stories about a half dozen Jewish families living in a small New Jersey town in the 1920s and none of them getting along with one another.
Even in political matters, there are jokes that the multiplicity of political parties in Israel reflects the many conflicting opinions and vigorous debates that occur among relatively small numbers of Jews. Also, British Jews seem to be more divided in their allegiance to political parties.
So why are American Jews today - if we take the Pew results at face value - so far to the left? A lot of it is brainwashing and mythology passed down through the generations, starting with immigrants from pre-Soviet Eastern Europe from whom the majority of today's American Jews are descended. Leftist ideologies were popular in Eastern Europe in the late nineteenth century up until WWI, the period of by far the greatest Jewish immigration to the US. And that cohort of Eastern European Jewish immigrants had never experienced the ill effects of Communism up close and personal, as much later Eastern European immigrants did.
"Higher criticism" was actually intended by its pioneers to be a vindication of chrstianity by showing that the Torah was (has veshalom!) a "Pharasaic" imposture written later than the Prophets, and that chrstianity was a "restoration" of this alleged original, "pure," pre-Torah form of "prophetic Judaism."
All this has been forgotten today. Now higher criticism is considered a nefarious plot against chrstianity, and most people don't even know the traditional Jewish teaching that every single letter of the Torah comes directly from G-d (in fact it is forbidden to reject a single letter of the Torah). This is now actually considered a "chrstian" concept (Protestant, to be precise) and most people think Jews don't have a dog in that fight.
Unfortunately, the Orthodox community is experiencing a great deal of turmoil with things like so-called "Open Orthodoxy" and the poisoning of the minds of even Charedi scholars by modern western academia. If you want to know how bad things are getting, just check out some recent articles at The Jewish Press, such as this one which celebrates modern academic theories and chides Orthodox Jews for their "fundamentalism" (notice that no one has posted a dissenting view). Then you have people like Lord Sacks (chief rabbi of the UK) saying that non-Jews need not leave their old religions and become practicing Noachides. In short, Orthodox Judaism today is under the same relentless attack that all traditional "western" religions are.
Similar to the issue of higher criticism, it is still actually normative Jewish teaching that the world was created in six days, though this belief is far from universal today among "centrist" Orthodox or even Charedim.