Miden spun off from Polygon to gain the independence necessary for launching its own token and building a dedicated ecosystem around the Edge technology, while Polygon shifts its focus to the AggLayer Breakout Program

Quotes that support claims

Khan said Miden needed independence as Polygon focuses on the newly announced AggLayer Breakout Program and a broader shift to an incubation model. "Additionally, launching a Miden token will give us the resources needed to build an ecosystem of projects and infrastructure providers centered around the Edge blockchain paradigm," Khan said.