> Mathematica notebooks aren't related to juypter.
I don't think that's fair. Rather, IPython, and later Jupyter, explicitly (successfully) sought to create a Mathematica-like notebook experience for Python.
I agree. The command line IPython by Fernando Perez was very inspired by Mathematica. He used Mathematica as a grad student and wanted a similar environment. In 2006-2007 Tom Boothby, Alex Clemesha and I wrote the first general used interactive web notebook called "The Sage Notebook", which became very popular with SageMath users over the years; the first version of Jupyter looked very similar to the Sage notebook. The Sage notebook was heavily inspired by everything around Google Wave and Google Docs (at the time), but definitely also by Mathematica's notebook. In particular, Alex Clemesha had recently been a physics undergrad and was a heavy Mathematica (and "Web Mathematica") user, and wanted a similar environment in a browser.