You're right that the CEO's goals may not be the idealistic goals I'm thinking of. The goals I had in mind were: be honest with your employees about something terrible and show them, don't tell them, that you valued their service to the company.
Judging by the contents of this email: the goal might be to confound or confuse counter-arguments to the decision, limit the damage PR-wise (and stock wise), and above all, insulate the new executive staff from a groundswell of anger/hatred from the bottom.
My instincts as a writer, and maybe a bit as a human being, is that you shouldn't try to fool the people who support you. If the author of the email (probably not Dorsey) was a stronger writer, and perhaps free of some pressures, I'd like to think he or she could have both been fair to those under him or her, and also protected from their wrath.
I too would be very interested in seeing historical examples of leaders forced to write messages explaining tough decisions. Would you happen to have any?