You can read the entire book here for free: https://en.wikisource.org/wiki/The_Protocols_of_the_Meetings_of_the_Learned_Elders_of_Zion/Protocols_of_the_Meetings_of_the_Learned_Elders_of_Zion

The book was widely distributed during the last days of Russian Tsardom, so it reached a widespread audience and led to violence against Jews. It was written to blame Jews (already a targeted group) for various societal ills to distract people from the oppressive Tsarist regime as a futile effort to destroy the Russian Revolution. This only intensified when Henry Ford (who was highly respected at the time as the epitome of the "American dream") published 500,000 copies of it for free in his newspaper, The Dearborn Independent. Many people saw Ford as a role model because of his early support for ethical wage laws and his lower class background and would therefore believe whatever he said.

The Nazis, who were inspired by many American policies such as the Native American genocides and American eugenics laws, sought to promote the book as a way to justify the deportations of Jews to ghettos and the Holocaust (which was kept secret from the mainstream German population). This consequently led to many neo-Nazis promoting the book as fact.

The book is still promoted today by governments in the Middle East and various parts of Africa as a way to justify wars against Israel and persecution of Jews. Since the book has been around for a very long time with significant acceptance, people are willing to embrace it.

As for why the Protocols became the go-to text on anti-Semitism instead of other books like The International Jew by Henry Ford is anyone's guess. However, the claim that the book was stolen from a synagogue and reveals hidden plots to destroy the world likely appeals to people who seek "forbidden knowledge" or "hidden secrets" in contrast to a more analytical text with less so-called evidence like The International Jew. In addition, the book's claims that Jewish people are using humanist and liberal ideas to brainwash people in the name of greed appeals to many government and political promoters of the book because there is often a significant overlap between prejudice and a demand for traditionalism. The Nazi German regime promoted an idealized and imagined German identity based on tradition, not unlike the viewpoints of many jihadist and Islamist groups today who seek an "Islamic golden age."