This is the likely cause - most software development is dreadfully boring. But at some point in a developer's career, they will have touched the monolith and everything is full of stars, and instead of saying "I'll just hook you up with Magento", they're like "I will build you an event-driven microservices architecture in a custom made C# framework" and disappear for six months while they work late nights.

(I wish I made it up. This was what a CTO at a previous project did. 30-odd people were waiting and churning on while he was unavailable because he had to indulge his own things. And once they were beyond the point of no return, both he and the manager that greenlit this project quit, but stayed on as independent contractors. I believe they were demoted or taken off the project and eventually gotten rid of when a new manager was found)