Partly due to frontend framework hype, I would say. If we take traditional backend web frameworks, like lets say Django, you could simply look for Django devs and would find plenty, even though it exists for a long time. Choosing a hyped JS framework is what is the risky move, because people jump ship quickly. There are design decisions in Angular for which I would never even consider Angular for development.
When angular.js came when you needed to do something highly interactive it's competitors used to be either amature hour hipster shit frameworks or hacking stuff using jquery.
