https://www.newsweek.com/this-what-true-friendship-israel-looks-like-america-opinion-1883323
By abstaining rather than an explicit veto, the U.S. allowed the Security Council to put Israel in the defendant's docket, alongside Hamas. It's an astounding degree of moral equivalency between an Iran-backed terrorist organization and the democratically elected government of the State of Israel.
Or, as Israeli Ambassador to the UN Gilad Erdan put it, "It was the Hamas massacre that started this war... Nearly six months has passed, and the Security Council still has not condemned the child-murdering rapists that started this war. The resolution just voted upon makes it seem as if the war started by itself... Israel did not start this war, nor did Israel want this war."