I would say Python frameworks like Flask or Pyramid offer the first 2 benefits as well, and when used properly in combination with a caching proxy and container server that allows asynchronous processing the 3rd benefit too. So they are not unique to Node.js although out-of-the-box, as a standalone application server, Node will be faster.
Which leaves the 'JavaScript comfort zone' as the main driver of Node popularity, which while understandable, IMO isn't exactly a technological benefit, rather a downside (I don't like JavaScript, at all).
- Easy to install and use, especially for hordes of client side developers.
- Easy to manage packages and dependencies via npm.
- Fast and scalable for writing logic around data transportation.