My interpretation of this as a manager is that this developer was probably a creative thinker with a decent track record who got stuck going down a bad path on this project, and nobody paid attention or intervened until it was too late. They were also probably pretty junior but perhaps had some past accomplishments that made them appear less likely to make this kind of mistake. Once it was in production, the developer very well may have been "stuck" with it (i.e., unable to get permission to scrap it and redo it, since it was technically working and solved some business problem).
Given the team dynamics and lack of involvement from this person's manager, I wouldn't move to fire them. I'd move to rethink the entire team, admonish the manager, and possibly remove them. The team itself wasn't working, and this was a symptom: someone had a bad idea, pursued it for too long, nobody did enough to stop it, and then they couldn't go back.
This is a classic consequence of a manager who has stopped paying attention to their own team. The team was most likely also overburdened with too many tasks, which is why everyone was working on something separate and independent and nobody knew what anyone else was doing. In reality this developer shouldn't have been given a project like this without being paired with a more senior engineer to supervise it, but that would cut down on the number of story points the team could get through and would thus be discouraged in a dysfunctional environment.