The answer is that they almost certainly built it with almost nothing hanging in the center, and without the dish below it. Once the basic platform was in place

The answer is that they almost certainly built it with almost nothing hanging in the center, and without the dish below it. Once the basic platform was in place, then they hoisted up all of the components to build out the 900 ton platform (actually, that took years and years as equipment was added to upgrade it). So, in essence, doing a replacement of all of the cables would need to start by essentially disassembling the thing completely and then rebuilding it.