I would guess it was extra insurance for CF in case Springer wasn’t able to CF as much. Probably they were thinking about a Merrifield/Tapia platoon if needed.
Also he’s cheap next year and there’s a decent chance he bounces back with the bat and is a good 9th man/bench piece.
I don’t think they expected him to be this bad, his underlying metrics were still good at the time of the trade I believe