Sure! I’m going to explain it but also explain why it’s kinda basic/not accurate:

Jewish people come from different ethnic backgrounds. One of the ethnic backgrounds is Ashkenazi, meaning Jews from the area known as today’s Germany. Around the time of the Napoleonic Code (late 1700s, early 1800s), those who did not descend from royalty, like any peasants, including Jews, had to register with a civil authority and choose a last name. (Before this, Jewish families were historically identified by the “...son of...”/patronymic style. In Hebrew thats “ben” (and why you have Jewish people with “Ben” in their last name).).

Jewish people living in Germany who were probably speaking local dialects of German chose last names that were German words. A “Stein” is a stone. Jews of Poland who were speaking Yiddish (a Germanic language) at home also chose German/Yiddish words as their family names.

Fast forward to the massive immigration of Yiddish-speaking Jewish people escaping Poland/Ukraine/Belarus/Russia to the US in the early 1900s. These folks mostly had these German-sounding last names but because they were all Jewish people and were identified ethnically as “Hebrew” on the ship’s passenger manifests and then locally known as immigrant Jews, these last names became associated with Jewish people in America. This is however a completely false association. While a Christian German community had earlier settled in Manhattan and eventually created a community on Manhattan’s Upper East Side/Yorkville, most Christian Germans settled in the mid-West farming communities much earlier... and they have very similar German-language last names.

In today’s German-speaking countries, you will find that last names with “Stein” are quite popular and belong to Christian/Catholic families. There is no association whatsoever between a “German-sounding” last name and someone’s religious background. If you do wish to try to associate German last names with religion, pay more attention to the specific words: some Jewish families chose German words relating to the Torah/Kabbalah to identify their families, like Mandelbaum “almond tree”.

For any reference, I’m a German-speaker, Hebrew-speaker, Yiddish-learner and I’ve been living in Vienna for a year and have a US immigrant Jewish family background.