Note the date is May 15, 2009. Nearly 4 months after the inauguration; some attorneys (such as Pat Fitzgerald stayed for casework.)
http://www.politico.com/blogs/under-the-radar/2009/05/obama-to-replace-us-attorneys-018390
In trump's case, "ousting" seems more on point; Bharara, who trump told would be retained, was simply fired. No orderly transition - of course Bharara was the likely target of this rushed "ouster" of all the attorneys.