I’m pretty sure the diagonal structures are just to make the bridge look cool. “Hey - we’re already over budget - lets get rid of that artsy stuff!”
I can’t imagine all the people involved that missed the critical features. Here in Seattle they had to tear down a 12 year old, 14-story building because someone didn’t dab epoxy on the ends of some steel cables - they started rusting through.
So the worker didn’t do his job, his manager didn’t, the company inspector, and the city inspector. (I might be missing someone.).
And I'm pretty sure one of our engineers will be along shortly to disabuse you of that notion ;-)
If there was any cosmetics involved, it might have been some type of decorative cladding on the cable stays.
There was to be two spans of that 'bridge', one over the road and the other shorter half over the canal next door.
The supporting pylon was to sit in a grassy area between the two, with the cable supporting both halves.
Not cosmetic at all, but - very obviously - absolutely necessarily, structurally.
See pic in #477 above