If Judaism is the oldest Abrahamic religion, why does it have so few followers compared to Christianity and Islam and why by such a large margin?

As a Jewish person myself its for a few reasons:

1. We don't forcibly convert, we also actively convince people not to convert (I mean using every argument possible to convince people). Jewish Philosophy states that if someone is holy enough to go out of their way to join they're holy enough to be Jewish (the conversion process is long and if it's not sincere they aren't accepted).
2. Jewish power structures have always been contained, in Israel for example Jewish religious leaders have little power.
3. Judaism has a long history of expulsions and being massacred, also forced conversations away from Judaism
4. Due to Jewish fundementalism its common to see people stop identifying as Jewish. For many people the Jewish community can be extremely hostile and unwelcoming, a few examples include: women, Neurodivergant people, Queer people, people without a Jewish education, people who dont fall into traditional gender roles/expressions, etc