Rashi’s Peshat Revolution – Was it an innovation “ex nihilo”?

Rashi was the first commentator in Northern France/Ashkenaz to write a ongoing Bible commentary that addressed the Peshat. Was this innovative breakthrough original to Rashi or did he cull from earlier sources? If so, which sources? What are the building blocks of his Peshat commentary and why did he feel the need to introduce this new style of Biblical interpretation?