What caused the decline of cursive handwriting?

In the very popular post Is Cursive Obsolete? one respondent unknowingly voices an opinion that so precisely highlights the mindset of American society.  A mindset that is even shared by the very people who love cursive handwriting and seek to preserve it:

Any writing that’s important will be typed up before it’s considered finished.

Mark Twain was perhaps the first well-known author to popularise the idea of the typewriter as a writer’s primary tool for getting words on paper, although it was most likely not his intention:

Please do not even divulge the fact that I own a machine. I have entirely stopped using the Type-Writer, for the reason that I never could write a letter with it to anybody without receiving a request by return mail that I would not only describe the machine but state what progress I had made in the use of it, etc., etc. I don’t like to write letters, and so I don’t want people to know that I own this curiosity-breeding little joker.
Letter, 19 March 1875

…I will now claim–until dispossessed–that I was the first person in the world to apply the typewriter to literature…The early machine was full of caprices, full of defects–devilish ones. It had as many immoralities as the machine of today has virtues. After a year or two I found that it was degrading my character, so I thought I would give it to Howells…He took it home to Boston, and my morals began to improve, but his have never recovered.
The First Writing Machines

Later such authors as E.E. Cummings, William S. Burroughs, Ernest Hemingway, among many others, would further underscore the association in the minds of Americans of machine-generated texts with “finished, polished” literature.

The fate of cursive handwriting was already set before 1910.  If a text written in a good hand was as important as the same exact text written on a typewriter, how could 89 separate typewriter manufacturers exist in the United States in 1909?

I sometimes wonder if this handwritten document would still receive the same celebrity status it has today if had been written on a Dell PC with Microsoft Word, i.e. today’s standard issue text authoring equipment of the federal government.