The bits I was aware of (/lived through), from UX standpoint was:

Mathematica -> iPython notebooks -> jupyter notebooks.

And from whatever source, I knew Mathematica notebooks had looked how they had /at least/ since the mid 90s. (My Mathematica days were college, and I did not spend much time contemplating the history of my tooling)

From elsewhere in the comments, it sounds like iPython->jupyter wasn't just a rebranding, as I assumed it was at the time.