Leaving aside those Orthodox who were opposed to the creation of the State of Israel, I think a major factor was ones comfort level winthin the community. While not insulated from the growing antisemitic tendency of late 19th and early 20th century, Observant Jews may well have felt a greater sense of community, coupled with a sense of isolation, than many secular Jews. Many of the wealthy and politically connected were late to the party too, those that could fleeing to the west.
http://www.shemayisrael.com/jewishobserver/archives/march/chareidim.htm
Report From Eretz Yisroel
Those Hated Chareidim
by Yonoson Rosenblum
I. Of Headlines and Footlights
It’s now official: chareidi Jews are the most despised group in Israel. According to the latest poll by Dr. Mina Tzemach, 28% of Israelis identify chareidim as the most scorned group in society.1 (Israel is perhaps the only country in the world whose citizens are asked regularly to identify which of their fellow citizens they hate the most.)...