I dont find it adequaetly explicable without malice. Israel has Gaza almost surrounded and exerts strong influence on Egypt and the border there too. The main task of the Mossad and IDF is to surveil and fend off Hamas and Hesbollah. And for Hamas the area to surveil is very small and they cant go anywhere else. Also Israel now claims hundreds of attacks on Hamas targets every day, which means they claim to know exactly where Hamas is. How can they not have noticed the buildup of material and forces necessary for such an operation?