Also, consider the amount of time groups like Hamas and PIJ have had to build an underground tunnel network to move people and armament near the border, for sudden large attacks just like two weekends ago.
Hamas has been in power since 2006, with any and all local government resources at their disposal, they can move a lot of stuff without any prying eyes seeing anything.
Don’t forget millions upon millions of low-information, low-empathy voters and non-voters who let it happen, many who still lazily believe that corporations are our friends, that “what’s good for walmart and Exxon is good for 'Murica”, that they are still the client and not the product, and the far-reaching implications of this.