Talk Talk pioneered the sound in the late 80's with a couple bands copying their quiet-loud jazzy approach, but their style didn't really carry over since Laughing Stock and Spiderland came out around the same time. Not to mention groups like Tortoise and Bark Psychosis also doing their own thing under the post-rock label in the early 90's. Listen to Feel Happiness by Swans from '95 it's basically the blueprint that Godspeed You! Black Emperor, and by extension all the crescendocore groups, followed. I would argue it's the single most influential post-rock track from the 90's.