To put this into perspective, it's worth noting that this was an issue of almost unprecedented contention between the US and Israel over whether or not to lift sanctions against Iran in exchange for nuclear disarmament. What Israel does to advance its foreign policy objectives is definitely within the purview of a foreign intelligence agency, and in this case the Israeli government was very actively lobbying congress. It seems pretty clear to me that the goal was to find out what Israel was doing, not spy on Congress.
Was the activity properly disclosed to the intelligence committees? Actually, NSA’s behavior with respect to Israel appears to have been briefed to Congress, as one would hope. “Convinced Mr. Netanyahu would attack Iran without warning the White House, U.S. spy agencies ramped up their surveillance, with the assent of Democratic and Republican lawmakers serving on congressional intelligence committees” (emphasis added).
The folks over at Lawfare had a much different breakdown of the issue: https://www.lawfareblog.com/why-do-conservatives-suddenly-so...
Relevant quote:
Was the activity properly disclosed to the intelligence committees? Actually, NSA’s behavior with respect to Israel appears to have been briefed to Congress, as one would hope. “Convinced Mr. Netanyahu would attack Iran without warning the White House, U.S. spy agencies ramped up their surveillance, with the assent of Democratic and Republican lawmakers serving on congressional intelligence committees” (emphasis added).