i also think elixir was hurt early by overselling of erlang and the erlang vm. a lot of the "groundbreaking" technology in the erlang vm was groundbreaking but in 1996 not post 2015. even now you can see people talking about how elixir makes parallel programming trivial when it's more or less trivial in all languages now (albeit via libraries or extensions sometimes and not natively). elixir's implementation is quite crude in comparison to some of it's competitors. the same goes for the "seamless distribution" that erlang/elixir proponents talk up. it's just a fully peered tcp mesh and a very simple binary encoding with a tiny rpc framework on top. it's something you could replicate in any language in a weekend (but you probably wouldn't bother. it's not very useful in a modern context). the promise very rarely delivered and people went back to more familiar languages
i think elixir had a brief window to get popular when go was still in it's infancy and nodejs was all written callback style pre async/await and java.util.concurrent was considered arcane knowledge but it failed to get a big enough community that could sustain it once go and nodejs and java got almost as good at concurrency as it was and didn't expect you to forget half of everything you knew about building and operating software. without a clear technical advantage people preferred the familiar