It occurs to me that Stone Temple Pilots were the flip side of the same coin. While Soundgarden helped transform grunge into pop, Stone Temple Pilots were a pop band ready to ride the grunge wave.
Both bands wanted to be rockstars, but only STP was open about it (which, in the early 90's world of indie-cred, drew plenty of criticism). The difference, per usual, came down to scene: Seattle self-identified as non-mainstream, and subsequently cool. Los Angeles (STP's home base) was an industry hub, and breeding ground of all things glam-metal and wannabe-rock. In LA, only success was cool, so STP was free to be rockstars on Day 1. Soundgarden had to be a grunge band to become a pop band; STP was always a pop band first, but with grunge adornment.
No coincidence, then, that both achieved their greatest success after the first wave of grunge crashed and faded. As soon as it was artistically viable, Soundgarden began creating arena-rock and Cornell became more Robert Plant, less Mark Arm. STP's second and third records immediately embraced all their pop influences, as disparate and ungrunge as the Americana-infused "Interstate Lovesong" and the mid-Beatles trippy pop of "Lady Picture Show," "Sour Girl," and even "Days of the Week."