"Black Hat" Community and Israel

I know and live around many "Black-Hat" Orthodox Rabbis and Yeshiva students who are very observant of mitzvos and knowlegable. Why is it usually that this group of people don’t move to Israel? Aren’t there Gedolim (ex: Rambam) who said that every Jew must live in Israel? - what do they have to say about that? I was told that they aren’t Zionist because they believe that Israel is a secular state - but don’t they see that the only way for it to become a more religious state is if religious people move there? Is the obligation of moving to Israel just a matter of opinion? Please help explain. Thank You. P.S. Are there any books about these different ideologies/opinions that you can recommend?

The Maharal (Netzach Yisrael 24) explains that in order to maintain the Galut, G-d froze the natural laws of history. In the natural course of events, a 2000 year long Galut would have been impossible: If the Jews were able to maintain their national identity they would eventually either rebel or return en masse to Israel. If their national identity were weak, they would crumble under the onslaughts of their non- Jewish oppressors. The three vows mentioned in Masechet Ketubot- not to rebel against the Gentile nations, not to make mass Aliyah, and the vow of the Gentiles not to oppress us too much- were not historical events but rather froze the way Jews and Gentiles thought. One result was that anytime someone would even raise the possibility of large-scale Aliyah, a good reason why this would be impossible or undesirable would always emerge to bury the idea. With the Ingathering of the Exiles of the last 150 years, this Galut-protecting mechanism has been seriously weakened but it has not totally disappeared. It is not limited only to what you call the black-hat community. It is sad to note how many religious Zionists still find reasons to remain in Galut. It is also worth noting that there are "black-hat" Jews in Israel who have come on Aliyah.