Judaism is what’s called an ethnic religion, rather than a universalizing religion. Ethnic religions generally don’t seek converts. There are accounts of forced conversion by Jewish fundamentalists in the Second Temple Period, but even then it tends to be of peoples they regard as ethnically related and ‘fallen astray’ rather than people they see as out-and-out foreigners. Ethnic religions are regarded as a pact between the Divine and a specific set of people - and outsiders are either viewed neutrally or negatively coming (or trying to come) into the faith. As such, ethnic religions generally only propagate by birth or, less often, intermarriage. They don’t want outsiders flooding into their private ethnic pact with the Divine, and, indeed, sometimes regard it as religiously offensive.

Universalizing religions, on the other hand, are quite explicitly peddling a view of the world that does not, theoretically, have ethnic or cultural borders. Christianity and Islam, both universalizing religions, desire Asian Christians as much as African or European Christians. Theoretically. There is a… great deal of difference between what is taught and what is executed, but in general you can assume that universalizing religions like those more or less always want a person as a convert, regardless of their background. The pact with the divine is regarded as personal, rather than ethnic, and the divine regarded as largely impartial to all the minute divisions of mankind.

Judaism tries to disincentive people to convert while Islam and Christianity both try/have tried very hard to convert people, often at the tip of the sword.

One thing no one mentioned yet.

Christianity really spread once it became Rome’s state religion, and Islam was always about expanding.

Once the Jews got kicked out of their homeland they were stateless people. Pretty hard to go against local religion when you’re a guest with no army.

They believe that God wants us to use our free will, which means that proselytizing isn’t kosher (har har.) Where Christianity and Islam have spread pretty aggressively (often literally), missionary work or let alone forcing people to convert is anathema to Judaism

Part of why is that Islam and Christianity spread to other cultures, often with force. Judaism doesn’t give heaven points like they do for converting someone.

I am not a historian but my bet would be that it’s ultimately a political question.

Christianity was the religion of the late and medieval Roman Empire, and later of the western European colonial empires.

Islam was a religion that became a caliphate and a series of empires afterwards.

There has never been a Jewish empire, and the Jewish kingdoms (Hellenistic Israel, the Khazar khanate, Beta Israel) have been small, non impetial and relatively short lived.

The Holocaust may have played a role

Looking at religion purely as a means of comfort for people who are afraid of dying, I wouldn’t think Judaism is very popular compared to Islam or Christianity because afaik, Judaism doesn’t have a clear way to heaven.

It’s because new religions always cherry pick the parts they like of old religions and then eventually replace them entirely. Judaism itself was just made up from parts of Zoroastrianism and Hellenism and Babylonian beliefs.

It’s all bullshit anyway so it hardly matters. Religions change as needed to meet the changing wants and needs of the people who follow them. A Christian from the time of the crusades would probably be horrified by what is considered to be Christianity today.