There was no thriving anti-semitism when he made his turn -- in truth anti-semitism in USA was in steep decline. His motives can be gleaned by this essay where he says the sight of a mixed couple fills him with a "disgusting prurience":https://www.commentarymagazine.com/articles/norman-podhoretz/my-negro-problem-and-ours/ …
Where are you getting this stuff from? His turn to the right was in 1970, after "My Negro Problem" & "Making It" (which has very few references to Israel. In any case, Commentary publishes articles praising colonialism, so they can't complain about it as a critique.