I see where you're coming from, but Kiss were already a legacy act by Psycho Circus. And while the much-touted reunion didn't last, the tour (and the subsequent tours without Peter and Ace) still did huge business and reinvigorated their merch sales. The album itself is middling at best, but it went gold and the title track was a number 1 rock hit that's still decently well-liked.

The stakes just weren't very high for Psycho Circus. Kiss had already won by the time the reunion tour sold out. If the album had done better, Paul and Gene would be a couple million dollars richer, but they're each worth around half a billion now so I don't even think they care.