From your link, in the last year alone Vue has had approximately a 5-fold increase in the number of downloads.
Describing this trend as "mostly flat with a slight upward bend." is very misleading.
Describing this trend as "mostly flat with a slight upward bend." is very misleading.
Go 2 years back on that page and you see a clearer picture, yes it did grow, but relatively contained compared to its competitors, specifically React.
And is it any wonder to anyone? I really ask myself. Would you go back to a stryingly typed templating framework with a complex api and ever changing ruleset, reliant on dependency injection and all the other stuff we went through with Angular? I don't think anyone would. It rather looks like Vue is catching the last remaining Angular 1.x refugees, but there isn't an ever increasing supply of those.
React has a self sufficient cross platform eco system. I don't think people using primarily web frameworks even realize the implications of that yet. React works outside of the browser, and not just natively on mobile but literally everywhere. Imagine you use React as you always would to make a native command line application (https://github.com/Yomguithereal/react-blessed), but now you want to have a store or move things around, so you `npm install react-redux react-motion` and you just apply it (https://github.com/gaearon/react-blessed-hot-motion). Look at the code and try to picture the overhead if you had to do this in C++.
Being able to transfer code and knowledge, and seeing new renderers pop up for the wildest platforms each day, as well as official renderers made by big vendors (https://github.com/Microsoft/react-native-windows), the idea of a web-bound Angular-like framework seems odd in 2018. I wouldn't expect Vue to get the same kind of popularity without at least competing or doing something new.
https://github.com/lyonlai/blessed-vue
Either way, it's not such an issue. It's not hard to build on React when you want react and Vue when you want vue. They're easy to pick up the concepts on.