Whittaker looks like a good man, but this job is way too important for taking chances.
That's why I thought the choice of Mulvaney was perfect.
Mulvaney is unquestionably very good.
But with Trump of course a lot has to do with chemistry—which is why I think it might have been Mulvaney asking for the “acting” title to start.
Either that or, again, Trump has in mind Whittaker when Whittaker comes available. Trump makes a lot of physical appearances—and might like the Hulk image.