I think that's a hard question. Node definitely helped evolve it. The idea of isomorphism was slow-growing (and yes, originally pretty rocky), but foundational to what we now see as web development. But if I really had to describe the start of the "JS obsession" by my experience, it would be the AJAX explosion, which led to the advent of the "web-based app". That very first moment of realization that yes, you can do anything on the web. It might be hard for a developer who started after that time, but functionality used to be relegated to windowed and console apps. In that world, you could imagine how useless javascript must have seemed - why do I need to write code to give "functionality" to what was basically seen as a remote pdf?

But then, I think there's no surprise to the fact every big company under the sun has some critical contribution to server-side javascript. Back then, most of the dev world were using Perl, Python, Ruby, PHP for their web backends (Java, VB, and C# were used, but too damn hard to write in). At best, those languages were non-ideal but reasonably comparable to javascript. At worst, some of those languages (Perl, lookin at you) were worse than javascript at all the reasons people make fun of javascript now.

It took a while to kick Rails off the "next big thing" podium, but it was pretty quick that Node was showing offerings that were just better than Perl-catalyst or early Python-Django. It's funny, Rails was the one with fancy ways to ship javascript from server routes (what a shit show that tech was) back when Node was establishing new best practices on non-isomorphic web apps. I remember when Hapi first came out, backed by Walmart. I then went from being a node hobbiest to believing it was the future. 1 year later I was running a scrappy little node team and we had this little $10M+ telephony app (of all things).