I think the hype is due to the fact that the literate programming thing is a good idea but many people haven't seen it before and there aren't many tools for doing it. I just wish I could use a proper editor with Jupyter. Editing in the browser is horrible.
It does support "sessions" which allow persistence across the code throughout the document (you could even have multiple sessions), but the wat it's done for Python is quite hacky. It uses an interactive Python shell so you have to write code as if you're using the shell (double returns etc.) There is a better way using ob-ipython, but after spending a long time getting it to work at all I found it not good enough. Using Jupyter kernels is the way to go, I think, but it would be a lot of work to get it working well with org-mode.
It provides an accessible, better workflow for common use cases than what most people were using before.
Sure, there are things out there that do a better job. Or are more powerful. But something which requires highly-custom config & training to be hyper productive on by definition means most people aren't using it that way. Same argument for Python as a popular language.