Flutter is all about being the last opportunity to sell Dart, and I doubt that Chrome (PWAs) and Android (JetPack Composer) teams are that happy about its existence, given the political answers when questioned about Flutter on their own Q&A sessions.
I don't think purely about Dart, originally it seemed to be aimed as a technically more robust cross-platform competitor to React Native. Its implementation has good merit in that regard.
That said, it may well not survive nearly as long as RN will, time will tell.
