Short version: Anti-Semitism constructs itself as a conspiracy theory about how the world works, and blames powerful shadowy Jewish figures for all problems. This invariably lands on any Jews who accumulate wealth or status (Soros, Rothschild, etc), though not restricted to them. https://twitter.com/daveweigel/status/1298413452013244417
The reason figures like the Rothschilds or the fictional Elders of Zion remain salient targets even today is that any conspiracy theorist seeking someone to blame for the world's ills is just one Google search away from centuries of material telling them that someone is the Jews.
So you might start out as free agent conspiracy theorist with no particular problem with Jews, but the deeper you dive into this world, the more likely you'll ultimately land on the Jews. Many conspiracy theories have followed this trajectory to anti-Semitism, as QAnon has today. https://twitter.com/Yair_Rosenberg/status/1298416448319238144
This is also why political discourse surrounding figures like Soros, Adelson, the Israel lobby or Israeli state can get so dicey. These folks are both fair game for legitimate criticism and also lightning rods for anti-Semites who use that critical discourse to launder bigotry. https://twitter.com/Yair_Rosenberg/status/1298415567829970944