Then we'd have the web relying on VBScript. If you stop Microsoft from doing that, well… the market was still changing quickly enough some other browser might've done it and got traction.
Microsoft would have eventually yanked VBScript, and we'd be coding in C# for the browser now...
You know, I think that wouldn't even be such a bad idea. It's got types and it's reasonably static, meaning it can be optimized a lot more than JS can - in fact, Dart was created in part because its more Java / C#-like structure could be run in a much more optimized fashion than Javascript could. And it was invented (iirc) by the guy who made V8, so if anyone knows anything about the limitations of JS's run speed, it was him.