I'd love to evidence what I'm saying with specific numbers since this kind of discussion would benefit from being as objective as possible. Sadly I don't have them. But I still believe what I'm saying and I have a few guesses about some of the causes:
1. Immutable data - so, so many bugs are caused by data mutating out from under you in subtle ways. If you write `x = 1` in your Elixir function, nothing can change the value of `x` except an explicit rebinding. You can then write e.g. `y = f(x)` and know `x` remains unchanged after. Note: this is also true even if the variable is a composite type. `my_struct = blah()` will remain the same in it's entirety no matter what you do with `my_struct`. This is different than in JS where e.g. you can change the contents of an object even if it's declared `const`.
2. Assertive style - the Elixir community favors writing things in an "assertive" fashion [1]. Briefly, this a way of writing code that will fail the moment an assumption is broken rather than letting the issue propagate.
3. Pattern matching (somewhat like destructuring in JS) - Elixir code actually ends up feeling "typed" with pattern matching. E.g. `%Time{} = today = Date.utc_today()` will attempt to bind `today` to the result of `Date.utc_today()` and will raise a `MatchError` when the result, a `%Date{}` struct, fails to be a `%Time{}` struct. Or `[a, b] = [1, 2, 3]` will raise a `MatchError` because `[1, 2, 3]` isn't a list of length exactly 2. You can use pattern matching to write very assertive code quite tersely.
These reasons are all local properties of code. But when all its parts are written in this way, a program as a whole gains a level of correctness that's hard to achieve in a dynamically typed language without them.
Also these reasons aren't exhaustive, but they're top of mind when thinking about this topic.
[1]: https://dashbit.co/blog/writing-assertive-code-with-elixir