While those community management issues probably didn't help, I don't think Elm's failure to break out can be placed purely on their shoulders.
The big reason why it - and all the other typed/functional compile to JS languages (PureScript, Reason, etc.) - remained niche is because TypeScript came along. It integrated with the ecosystem more seamlessly, was instantly comfortable for JS devs, and was backed by MS who gave it first-class support in VSCode. Arguably TypeScript is not as good as those other languages, but none of them are better enough to overcome those network effects.
The big reason why it - and all the other typed/functional compile to JS languages (PureScript, Reason, etc.) - remained niche is because TypeScript came along. It integrated with the ecosystem more seamlessly, was instantly comfortable for JS devs, and was backed by MS who gave it first-class support in VSCode. Arguably TypeScript is not as good as those other languages, but none of them are better enough to overcome those network effects.