A few reasons, which I alluded to. He offered a grand vision for a highly-configurable system. This vision meshed with the directors desire to have such a syst

A few reasons, which I alluded to. He offered a grand vision for a highly-configurable system. This vision meshed with the directors desire to have such a system. He was effective in promising all of the features of such a system that the director wanted. In fact, he promised even more! To be fair to him as a developer, he was trying his best to deliver on this promise. The system as promised was beyond what he could produce. Within the giant mess he had created were many of the elements required for the grand system, they were just buried underneath very complicated XML systems and over-engineered code. He would prototype new system features working (held together with digital tape and bubble gum) to prove viability. The fact that these features were incomplete would be hand-waved away. Of course, sooner or later the system would have to be "filled in" so that all of the details were correctly handled - which would inevitably require further massive rewrites to all systems. This gave a feeling of progress but that progress was actually hollow. If anyone pointed out that most of the systems he was implementing were basically prototypes and would fail on any case other than the ones he used as examples - he would become extremely toxic. I mean, literal yelling matches. His tactic was to belittle anyone who pointed out issues in his design or his code. Most of the developers on the project were junior so they didn't stand up to his tirades, the rest just didn't want to deal with it. I have no idea why the director allowed that behaviour to continue but it was a regular occurrence. This meant that his examples worked barely enough and no one else could get their own code working without his input. That matched his toxic rhetoric that everyone else was just getting in the way of him getting things done. It also gave him the cover to work late nights when no one else was around, so no one would interrupt him while he completed this grand system. This attitude of "I am so great that others are getting in my way" is now a huge red flag for me. If your attitude is "once I'm done my grand system, everyone will thank me" then I want you off my team. Your grand system will never be done and if you develop it in isolation I can guarantee it will be of no use to anyone. If you react to feedback about your grand system with "you are too stupid to understand it" then that is even worse and I cannot get rid of you fast enough. If your system cannot be understood then that is your problem, not a problem for everyone else. The fact that someone with either of those attitudes is seen as "brilliant" by anyone is a mystery to me.