To be fair elixir has slowly become more and more static over time, as in via convention and tooling.

Even at the language level, every single variable is a constant—the opposite of "hyper dynamic".

The larger design patterns build on that immutability on the local level. Inheriting the design patterns from Erlang/OTP also make larger programs much more feasible. I can be away from a piece of Elixir code for months and come back and the structure is usually pretty straightforward to pick up again. Primarily due to supervisor hierarchies combined with the lack of weird OOP hierarchies and entanglement.