I think it is even simpler than that. Populist parties need to have a simple message that their supporters can easily understand. Having two quite different enemies at the same time would make things harder.

If there were 0 muslims in Germany today, their politics would be 100% about Jews controlling the world and all that stuff.

There is no confusion: Hannah Arendt and Albert Einstein famously denounced the right-wing tendencies of Israel in 1948 in a letter to the New York Times:

"Among the most disturbing political phenomena of our times is the emergence in the newly created state of Israel of the "Freedom Party" (Tnuat Haherut), a political party closely akin in its organization, methods, political philosophy and social appeal to the Nazi and Fascist parties. It was formed out of the membership and following of the former Irgun Zvai Leumi, a terrorist, right-wing, chauvinist organization in Palestine."

The leader of that party was Menachem Begin, later prime minister of Israel and founder of Likud, Netanyahu's party.

I'm convinced that many right wingers pretend to support Israel while being secretly delighted to see the country heading deeper into trouble. It serves as a convenient disguise for their antisemitism.