I would guess they want the Critical Roll crew to get paid, and there are far better ways than passively giving them watch time on a streaming service.

Edit: I don't follow them, but maybe they have a patreon?

Edit 2: I just realized that since they distributed through Amazon, they probably can't distribute their own content. So sail the seas or feed the beast, I guess.

I got my start in print publishing via Amazon and they pretty much own whatever I published through them. It's easy to jump in, difficult to climb out.