I kind of wonder whether the Clippers might have been trying to play mind games, leveraging the upcoming midnight deadline to try to extract more loot from the trade. Instead of panicking, the Wizards and Celtics told them to kick rocks and pulled in Memphis instead.
A guess, admittedly. Probably it's much more innocuous than that and it was simply a matter of the Clippers backing out when it became clear that they wouldn't be able to get Brogdon in for a physical in time. But I like my reality where all of the other franchises are cartoon villains and we alone are virtuous and intelligent. It's fun that way.