What is bottleneck theory of constraints?

Example: A senior engineer handles all production deployments because 'it's faster if I just do it.' Within six months, every release depends on their availability, the team has learned nothing about the deployment pipeline, and the engineer is burned out, working weekends, and resenting colleagues who leave at five. The engineer didn't fail to delegate because they were selfish. They failed to delegate because every individual decision to 'just do it myself' was locally rational. The system-level failure only becomes visible when you zoom out.

This concept is part of Delegation Patterns in the How to Think curriculum.