@Penguin very nice round up
Also Atari Corp. biggest mistake was not to release more powerfull computers betwen 1985 and 1991 (Atari TT). They start 68020 computer right after ST, talk in press about it, but failed to deliver until 1991.
One reason is that Shiraz Shivji left Atari Corp. (Roy Good took over development) and other reason (my guess) is that Jack "retier" and gave Sam Tramiel his role.
I am pretty sure that no one on planet could do what Jack do: make ST in such short time. He organize everything! Enginiers left Commodore (and many, many others) because of him (they believe in him), he was called by Warner Atari because of his reputation, he made great deal with them to take over Atari, he manage to scrap enough money to start production... Simple briliant!
Thanks to him I (and many other people) could buy GUI computer in early 1986 with brilliant mono, 71Hz monitor for work! Software starts to appear in 1986... Otherwise we would need to wait for Amiga 500 (price reduction, but still with terrible monitor for long work!) or would need to sell kidney to buy a Mac (with ST we got almost for free much better and faster Mac!