It wasn’t the original design and build but the lack of maintenance that brought it down.
The "company" that owned and operated it was a government entity until privatized in early 2018. Their first act on privatization was to start a massive renovation project. They just didn't act quickly enough. It was government for too long.
The original design made the bridge difficult to maintain. Morandi encased the cables in concrete, so the corrosion could not be seen or repaired.