Stars per year is always going to favor newer technologies. Which is why I believe this metric encourages framework churn.
True, but there are other frameworks that came around the same time and have not reached the momentum of Vue.
Two factors why VueJS is popular: 1. It is adopted by PHP Laravel communities as the goto framework for frontend 2. It is adopted as underlying for Weex framework (similar to React Native) by Alibaba. Which makes it adopted fast by developers in China.