Since honesty is a theme of this thread, let's be real here. PgSQL is popular now only because Oracle killed MySQL.
This is not to denigrate the work of the Postgres team -- it's easily one of the best-managed open-source projects and my admiration for them is immense -- but ~95% of the time, the tech stack is chosen as a fashion statement.
MySQL was fashionable until Oracle showed up. Postgres has been trucking along for decades and has essentially won by default. I don't know if there are many great marketing insights to take away, other than "stay out of the way of the $50B gorilla".