Second question is too involved for me. As for the first question, there are a few reasons:

• Judaism is simply not a proselytizing religion as Christianity and Islam are. Jews don't try to get you to convert to Judaism, or send out missionaries. Christians and Muslims do.

• The long list of rules - the Law - that Orthodox Jews have to follow is a pretty big disincentive to conversion. At least part of the reason that Christianity took root with gentiles is that Christians are not, by and large, obligated to follow the Law.

• Christianity and Islam both had a whole host of historical circumstances that led to their ascension, and which Judaism never had. Christianity became the state religion of the still-powerful Roman Empire in the 4th century. Muhammad unified the Arab tribes, which led to their massive conquests in the 7th century. I don't know exactly how powerful of a regional player Israel and Judah were before their conquest in the 6th century BC, but they certainly never had anything like the global influence that Rome or the Muslim states did.