I'm going to have to admit and confess to some ageism here on this one.
When I saw that, IMO, Warren Beatty has not aged well and was seeming to have a hard time reading the envelope or struggling with the name, that he was simply having quite the senior moment (temporary dementia maybe), and that's why it ended up being such a fiasco. The irony is that I wouldn't be surprised if it ends up being some twenty-something production assistant working for peanuts who made the mistake.
In the long run, it's a silly and embarrassing moment for the Academy and the Oscars that is meaningless in terms of its actual importance, but it's too bad that it will come to be the defining moment in what I thought was otherwise a very well done production with a good host and some good speeches. It's really a shame that no one is talking about Viola Davis's acceptance speech today; that was a timeless classic.