Ever been under a missile attack? If you’re lucky you get a warning. Then you move your family to your homes safest place and wait. You either hear a boom or you don’t. And if you do, you tell your family to wait because there might be another one. It’s terrifying. Of course, it’s more frightening when you don’t get a warning and your neighbors house just blows up.
That’s just this instance. I took the question to mean why the Israelis amplify their war with Hezbollah.
This instance with Nasrallah was probably a matter of use it or lose it on the intelligence side. They got information and acted on it as fast as possible.