It seems to me that by appointing another Jew, Rosen, to replace Rosenstein, that Trump is trying to take advantage of traditional antisemitism. In other words, many will say "You see the power that the Jews have in Washington D.C and the Trump administration?, and similar comments.
This tactic has been used throughout history, especially after W. W 2 in Eastern Europe. The Soviets put many Jewish communists in high ranking positions, counting on the fact that antisemitism would anger the people. Thus, the locals would be more upset with the Jewish communists than the Soviet Union /Russia.
If you ask me, the end result of a move like this, i.e appointment of Rosen to replace Rosenstein is an increase in antisemitism from both the Right and the Left. The Left would say that this why the Palestinians aren't treated fairly, while the Right and Left would jointly question the extent of Jewish influence in Washington DC, and its' effects.