The only thing I can figure out is old habits dying hard.
They just can't let go of the notion that the Democrat party is liberal despite all the evidence that it is anything but.
The history of American Jews and the social progressive movements is long and complex. Many American Jews are descended from European refugees in the 19th and 20th Centuries fleeing persecution and full of utopian ideas for their new home.
Jewish immigrants were at the forefront of the labor movement, the suffrage movement, and the civil rights movement. During the height of those movements, overt anti-Semitism was still quite acceptable in American society and despite the significant contributions of Jews to those movement, many others involved were hesitant to acknowledge those contributions for fear of having their cause being associated with "Jewish Intellectualism".
American Jews, on the other hand, tended to ignore lack of acknowledgement in a deep desire to be accepted and laid the groundwork for liberal hatred of Israel by doing so. One can never respect one whom you've slighted.
On the other hand, the fastest growing segment of these American Jewish community is the Orthodox / Observant congregations of Judaism. These segments don't have the long history with American Liberalism as Conservative and Reform Jewish congregations that were willing to throw out observant customs in a desperate bid to assimilate. The Orthodox Congregations tend to be more politically conservative and less forgiving of liberal attacks on Israel and American Jews.
What you are seeing now is more and more outspoken support of Israel in the Jewish community, particularly when those attacks come from political segments that Jews have traditionally supported.
One more thing, don't put too much faith into things you might read that 80% or 90% or whatever number they choose to make up being supportive of liberal candidates. There is still a strong stigma in liberal Jewish congregations about openly opposing their traditional politics. Many Jews might poll liberal while actually being quite conservative in their hearts.