When I first heard about Gutenberg, I asked some people at WordCamp London and later at WordCamp Europe who had requested it.

There appears to be some short memories. Pretty much everytime the editor comes up here, there is a long discussion about how it needs improving. For example.

There are long discussions on Trac tickets which have been going on for years about how the editor experience should be changed.

So, in answer to the question "who requested this" - the community did.