Elm was very heavily evangelized for a while, and people were using it. Had there been a migration path through the breaking changes, it would have been a lot less disruptive.

Even if there had just been incremental bug fixes, I suspect between some and most people would have gotten over it, but seven years of silence is a very long time- long enough for an entire generation of new developers to start calling themselves seniors knowing only that Elm has stalled and shouldn't be used, because the controlling developers are unreliable and prone to giving the appearance of abandoning the language.