What I find unusual is - according to the infographic - both southern cables broke in the initial stage. And then that was followed by the northern cables break

What I find unusual is - according to the infographic - both southern cables broke in the initial stage. And then that was followed by the northern cables breaking in response to the load shifting. I presume the two southern cables are independent components and support independent platforms. Why would they both break at the same time, if not for some exogenous event?