Why have some young US Jews turned against Israel?

JPost One-on-One Zoomcast, Episode 26: Jeremy Sharon with Shmuel Rosner, fellow at The Jewish People Policy Institute and expert on Diaspora Jewry.

JPost one-on-one Zoomcast: The Jewish People Policy Institute (JPPI) fellow Shmuel Rosner.
A recent poll of the US Jewish community produced some startling results about the level of attachment, or lack thereof to the State of Israel for a substantial segment of American Jews, particularly young Jews. 
According to the poll, conducted by the Jewish Electorate Institute, a liberal-leaning organization, on a sample of 800 American Jews, 25% said they think Israel is an apartheid state, including 38% of under 40s. 
Additionally, 22% said they believe Israel is committing genocide against the Palestinians, with 33% of them under 40, while 9% –20% of them being under 40 – said they don't think that  Israel has the right to exist. 
Speaking to The Jerusalem Post’s Zoomcast series, Shmuel Rosner, an expert in Diaspora Jewry and a fellow at The Jewish People Policy Institute (JPPI), said that main reason that these Jews have become distanced from the Jewish state is that that they have become distanced from Judaism. 
“The fact is that those who are not associated with a Jewish denomination or whose tendency is to be distanced from Judaism are also distanced from Israel,” says Rosner. 
The analyst opines that some of these people might be permanently lost as a demographic who could support or feel any affinity to the Jewish state, but argued that the most important to address is the foundational problem of a lack of connection to Jewish life. 
“The work that needs to be done is making younger Jews attached to Judaism. If Jews in the US keep their affiliation with the Jewish community at large, I’m talking about living an actively Jewish life, then I’m not that worried about their attachment to Israel, this will come as part of the package," he said.