Possible meanings are 1) following the idols was in itself detestable behavior or 2) because he followed idols he engaged in other detestable behavior.
Here "Israel" refers to all twelve tribes of Israel and not just to the northern kingdom. Alternate translation: "removed from the presence of the people of Israel" or "drove out of the land before the people of Israel" (See: [[rc://en/ta/man/jit/figs-explicit]])