The US has been pressuring for restraint behind closed doors while offering unconditional support in public from the start. Honestly, they haven’t even seemed to be trying too hard to keep it a secret as details of closed door talks have been leaked almost in real-time. Democrats don’t like Netanyahu, who’s aligned himself ever closer with Republicans over the years, and see both him and his policies as impossible obstacles to peace, so it’s seriously unlikely they’re doing it for his benefit. I’m sure it’s partly to help restore a sense of security in a traumatized Israeli public but it’s probably primarily messaging for others in the region. They don’t want to give the impression that there’s any daylight between the US and Israel so Iran/Syria/Hezbollah won’t get the idea that it’s worth gambling that the US won’t act if they attack. Especially if Hezbollah decides to go to war, everything will become exponentially worse for everyone involved, including the Palestinians.