I don't think that Devs making those chooses but business and industry forcing devs to explore other options. One of the main issues with Scala currently that is no good selling story anymore for a business peoples. Even Rust story with 'memory safety' very fragile because not a lot of businesses see it as huge issue which worth additional effort (probably only MS backing helps there).

In the past it was lot of selling points that business could see:

- 'better java' - more velocity over java without loosing anything

- 'type safety / FP' - less errors that cost money in production (backed by 'Typesafe/Lightbend' company)

- 'akka' - platform for distributed/concurrency applications (in pre kubernetes era was big demand for it)

- 'spark' - initially Scala was only way to use it fully

- 'twitter' - startup success story

- and few more

But now nothing from this list has any real meaning for peoples making decisions currently.

Kotlin actually suffer from this too as 'better java' not that big deal when java constantly improving.

I can't even describe how much I dislike SBT.

There's definitely less Scala jobs on the market these days.