Literally explains how Mufasa never expected this to happen

I just thought it would be self explanatory that Scar was up to something here for Mufasa. Assuming the brothers weren't as close judging from the literal first scene with the both of them in the movie, Mufasa would espect Scars scheme. But from this scene in the new movie where Scar saved Mufasa in the first place explains that somehow.