TIOBE is a famous benchmark, but it is also completely useless.

There is a lot of legacy code out there that skews the benchmark, making the index an unreliable indicator of a programming language’s current popularity or the volume of active development in that language.

You'd be hard-pressed to find a job where you can program Fortran or Assembly Language all day. It's a lot easier to find one where you can do Kotlin or Rust.

Kotlin might not be as popular as one would hope, but that is not something you should conclude from the TIOBE Index.