Sure, it was an embrace-and-extend move, but I'm not sure it was a bad idea even so.
What I'm getting at in a somewhat snarky and roundabout way is that VBScript killed multilanguage support in browsers.
There is hardly any popular language today you could embed and get better performance than JS anyway, except for Lua, which barely qualifies as 'popular'.
Meanwhile there are a hundred cross-compilers/transpilers out there that give you the kind of syntax you want, without requiring a ton of changes in browsers.
PDF: [http://research.microsoft.com/en-us/um/people/emeijer/papers...]
Language fanboys might bash javascript, but there are many examples of the great things that can be achieved with javascript that make them look really quite silly, and every language has its pitfalls. Javascript is not a bad language, but it is misunderstood and people who misunderstand it are the most vocal detractors.
Opening up the browser to many languages causes the tower of babel all over again. Now front-end devs won't just be required to be a "javascript ninja", they will now have to master many other languages in addition to all of the DOM wackiness that comes with supporting multiple browsers. It's all just too much.