I agree it doesn't make sense, but his stats in the 9 games since then have little do w/ that. 9 games is way too small a sample size, and it's not as if moving one spot down in the order, Ryan Braun is suddenly going to say, "OMG! So much pressure, I'm the cleanup hitter now! I can't take it!" and break down sobbing and swinging at every down and away slider he sees.
The reason the switch didn't make sense was b/c Braun's speed is better suited to the 3-hole, where you traditionally put your best pure hitter. The 4 spot goes to your best power hitter, which Fielder obviously is.