Because of literally years of terrorist acts from Hamas? Because the action initially had overwhelming public support? Because, as any military action without proper planning, they promised a quick victory and had no plans beyond "bomb, bomb, bomb"? And had no plans for "what do we do if we don't succeed"?

For an exactly same "military action with no planning but a lot of bravado" scenario see Russia's invasion into Ukraine.

Because there were children to starve. Brown children.