Not knowing anything more, I would suspect rusted rebar was used along with substandard concrete or incorrectly set. I’ve seen bridges in Pinellas County FL built with rusted rebar. Huge rust streaks pouring down the concrete sides. The marine salt environment is very hard on bridges. When rebar rusts it expands and cracks the concrete. Once the rebar is gone the concrete loses strength.
It appears to be segmental construction from the photos. If that is the case, rusted rebars are uhlikely to be the culprit. Not knowing anything more, I suspect failure in the post tensioning system, either in the tendons or the supports. Or could be a foundation issue.