Agents enter dual agency when they represent both the seller and the buyer. Dual agency can happen even if the there are two agents involved -- a listing agent and a buyer's agent -- if both agents work for the same broker. That's because it is the real estate broker who creates agency.
The notion of Jewish control of the United States is utter nonsense. Jews are a capable people who have, through hard-work, gained a disproportionate role in some aspects of American life. But they in no way dominate the country.
This period of immigration came to an end with the passage of restrictive laws in 1921 and 1924. Jewish emigration from Eastern Europe to the United States never again reached the levels that it did before 1920.