Think of the developers as players competing against each other trying to get their ideas (PEPs) incorporated into the language, seeking individual recognition, credit, etc., and also think of languages competing against each other for developer attention, and then it will make a bit more sense why I called it a "Nash Equilibrium" :-)
Nash equilibria are mainly interesting when they are not Pareto optimal. Both the developers and users of a language, if being rational, should prefer languages to be on the Pareto frontier, but where on that frontier depends on how you weight the trade-offs.