Why did the US seem to undermine the possibility of an Israel Hamas negotiated ceasefire and hostage release?

Recently the US chose not to veto a ceasefire resolution in the UN Security Council. It seems as a result, that Hamas immediately backed out of negotiations with Israel and others, that if the negotiations had succeeded, would have called for, a ceasefire, and the release of Israeli hostages, and the release of many hundreds of Palestinian prisoners being held by Israel. Why did Hamas back out of negotiations? My guess is that they decided that their plan to foster world outrage towards Israel, because of the civilian deaths in Gaza, was working, as seen by this latest UN Resolution. This is in spite of the fact that only Hamas reports civilian deaths in Gaza, and further that Hamas was complicit in causing many civilian deaths because they have been using Gaza civilians as shields. I suspect that Hamas was thinking that they could count on this growing world outrage, to get Israel to back out of their commitment to attack Rafah with an IDF ground offensive. And that meant that Hamas didn’t have to negotiate any longer with Israel. I wonder, why couldn’t the US see, that there lack of a veto of the ceasefire resolution, would cause Hamas to stop negotiating with Israel? I am a novice at understanding the UN and complex world affairs. But, I do understand the impact that an effective public outrage campaign can have, which has been Hamas’ forte for many years. Doug