It's pretty simple. The initial years of the peak, while certainly somewhat robust ratings wise, were not comparable to the audience that KMXP (Mix 96.9) had garnered. I agree that the Peak up until about 2007 had a great sound... aside from the slight over-modulation in the mid-range of the audio-chain which continues even to this day, but that's just the sound guy in me. Incidentally, those initial years of the Peak had a great sound because Joel Gray was the PD, the on-air jocks were a bit different--and to the conventional radio listener--were probably a bit too relaxed, but a slightly different kind of sound nonetheless. They began mixing in newer tracks and leaning more Modern AC after 2007 in an attempt to grab some of KMXP's audience... based on the PPM (and old arbitron) data it could be argued that the format tweak wasn't really all that successful in doing what it had set out to accomplish.
The Peak continues to have reasonable numbers and is still a fair station there's no doubt, but it does seem to lack a bit of the flare that it had when it signed on... then again, anything would be an improvement over the old and dreary KKLT. Blah!