Maybe it wasn't, but being able to declare the UI as a function from state (viewmodel) to DOM just once, and never having to manually patch the UI to get it to

Maybe it wasn't, but being able to declare the UI as a function from state (viewmodel) to DOM just once, and never having to manually patch the UI to get it to the right state... is a huge development time saver. Angular did the same but went on a different path: watching the state (scope) for changes and then digesting the resulting spaghetti updates React users are simply adopting well known techniques from functional programming languages because they work well with the virtual dom concept. Except for that concept, there is nothing new being invented here.