It was born at the same time as webgl, at the time of Jit optimisation for js engines. As a subset of js first, then as wasm as we know it. It was originally for games and performance on the web.
At no point there was a conversation about "replacing js", but more like, "js can't do these stuff. let's have something else".
There absolutely was. This famous talk was made even when it was still Asm.js:
https://www.destroyallsoftware.com/talks/the-birth-and-death...
All I can tell you with certainty is that the people who designed and funded webgl/asmjs/llvm efforts at Mozilla (Alon, Vlad, Brendan, …) clearly understood that wasm was a needed companion alongside JS (and its DOM&co bindings). Not a replacement. I was part of these conversations.
I understand why people would think it was a JS killer, but that's a naive way of looking at it.