The Risan scientist said that it appears to have been sent through a tunnel of sorts in space-time, which could tie into the anomaly being created during the Temporal Wars and originating in a previous century.
The scientist also theorized there was an object at the center of the DMA and it was mentioned Starfleet was working on a next-gen Spore Drive. I'm wondering if something goes a bit fucky with it in the future when they test it and the end up creating the DMA? It would also explain why the DMA is able to "jump" without warning. Plus, it'd be kinda poetic for Stamets to find out he's sorta responsible for creating the DMA while swearing to Book that he'd find the source of the DMA.