It just makes sense. Both are damaged goods to a certain extent, but would only help the drawing power of that show. On paper, it would make for a good fight since Mir probably doesn't have the knockout power Bigfoot or Browne have, and Overeem is decent enough on the ground where even if it went there it could still be exciting.
If Overeem gets the win, it provides some redemption over a top 10 fighter and restores some of the shine he lost. If Mir wins, it snaps that bad losing streak and keeps him relevant and in line for big fights.
As for the loser? I think we all know the answer to that question.