It's as simple as that.
Its success has nothing to do with looking in the other direction or not redefining Javascript: it solved a problem that a lot of Javascript developers were struggling with.
Now what's really fascinating to me now is that while one can safely say jQuery created a revolution in the Javascript world when it came out, it is today widely looked as a smell and avoided as much as possible in favor or frameworks that modify the model instead of the UI.
And this quick rise to success and fall to obscurity could very well happen to the successful frameworks we are currently using today (including React).