Core Vue contributors (especially Akryum) have worked on the integrations for Vue. I don’t know the history of how React came to be a part of Meteor and if core React members made it possible or if MDG helped out, but I imagined the community carried the torch for it as well.
First-class view layers other than React should be up to the community (maybe Angular can be up to Tiny as well, not sure)
Still don’t understand why you think they should be maintaining the React integration but leaving everything else up to the community. It’s up to Tiny whether or not they think supporting the existing integrations is important.
It’s been mentioned in here already, but the creator of Vue worked for MDG and it has been argued that it is an even better fit for Meteor than React. My point is that Meteor can be successful while not favoring one view framework over another.