Hmm. I thought part of the deal with Stitcher is it allowed podcast producers a channel for monetizing their pods without having to have any knowledge of being a SEO or Ad expert. Now that they're moving the content over to SiriusXM, seems to me you're reducing the size of the market (listeners now have to be SiriusXM subscribers, and despite being a large market, that's still a smaller market than "anyone who can download the Stitcher app") and you're reducing the ad revenue stream (not all SiriusXM channels have ads.)
Maybe you don't have to be a SiriusXM subscriber to listen to content you previously got through Stitcher?
Maybe Sirius has some other revenue stream to convince independent producers to stay with the venue?