C. 2015 one of my friends was a Django dev but moved to Express/node because that's where the cool kids went, it was one less language, and allowed them to move logic FE->BE and BE->FE much easier. Also, a bunch of Rails people left to Node/FE JS and Rust (BE). JS/TS is still an irreducible requirement for FE. There is no law that either grand unified frameworks must be used nor entirely separate FE and BE must be maintained separately and are somehow mysterious, arcane arts. Not sharing code when/where it is possible and appropriate is duplicating effort.. like client- and server-side input validations doing exactly the same thing.
The only reason I touch JavaScript on the backend instead of .NET, Java, Go, Rust, OCaml, Haskell,.... are SDKs and customers that don't let other option than JavaScript all over the place.
Thus my point of view is that I couldn't care less about competition between JavaScript runtimes.