Not sure it would have been possible to attach cables to only the part which was hoisted over the traffic lanes, without the other half cabled to the central tower simultaneously.
But then, why didn’t they erect the other half first?
Can you find “what is missing”?
If you look at the way the cable connections are angled, the post on the left IS the center post according to the rendering. It looks to me like the other part of the bridge as well as the support tower and cables were not in place.
From the drawing, the tower is in the middle of the structure. Only one span of the bridge was set in place. The suspension cables couldn’t be put in place until the opposing span was in place.
I don’t know how they thought the bridge span could be left in place unsupported in the interim.
IMO this is a ridiculously elaborate and ostentatious bridge for an overhead walkway. Such things are usually reserved for spans across large bodies of water.
Top photo of bridge makes a lot of sense to this non-engineer and is more appealing to the eye.