In a sense, they did: everybody wrote Javascript frameworks, instead of writing new languages which compiled to Javascript.

But all kidding aside, it's hard to predict in advance which cool-sounding ideas are actually cool, and it's very hard to maintain a best-in-class tool if you're willing to merge concepts that haven't been battle-tested elsewhere. This is another reason jQuery won: its plugin system gave it a way to cultivate ideas that could be awesome but that weren't yet ready for the big show.