John Fogerty--What happened?

Cranked up CCR's Willy and the Poorboys today (more fallout from the Cobain book--one of the photos shows a messy ol' rockpad of Kurt's with a Creedence record sticking out of a crate), having programmed its great lost threesome ("It Came Out of the Sky," "Don't Look Now," and "Effigy"), I began musing on the great Fogerty quandary: where did that lyrical edge go? A few decent toons came after Willy, but his first two solo albums of the '70s were almost all covers (not badly rendered at all, especially the Charms' "Hearts of Stone"), and since the overrated "comeback" of Centerfield he's really been good for, well, nothing...other than cannibalizing his old group's inimitable musical style. Fogerty's writing genius seemed so uncomplicated that, as long as regular guys kept getting screwed, he could last for ever--especially with that voice. And with the resurgence of roots-rock over the past 20 years or so, you'd think he would have been inspired, regenerated, nay, compelled into relevant action. Haven't heard the ominously titled Deja Vu All Over Again yet, but the man ranks up there with Sly Stone, Rod Stewart, and Johnny Rotten as guys with prodigious gifts who just...lost 'em. Maybe getting disconnected from the band rattled him out of his rhythm, or maybe the band contributed the special fuse that made the machine really hum. Or maybe (excepting Johnny Boy) there was something about '72-'73 that took it out of these guys. Any theories out there?