Justin Turner didn’t seem like a good fit for the Cubs given their current circumstances, so it wasn’t surprising in the least that he signed elsewhere. Though adding a veteran who’s still very capable at the plate is never a bad idea, Turner is mainly a DH at this point and probably won’t play third base in anything other than an emergency role. He’s also a right-handed hitter, which isn’t ideal for the Cubs even if you consider his excellent platoon splits.
The other wrinkle here is that Jed Hoyer probably would not have considered the same $13 million guarantee Toronto was able to offer.