SD, on the whole, had been horrible for pretty much all of Eddie's title reign, which of course is going to pull his number down. when he was a midcarder, the shows were significantly better, meaning more people were watching.
JBL was working primarily against Eddie, so JBL's numbers would appear to be helped out by that fact. Now that he's working with Taker, I'm sure those numbers are going to stay higher than they would normally be.