Maldonado has a 0.5 fWAR in 289 PA this year.
Contreras on the year is at 2.2 fWAR in 340 PA this year.
Caratini on the year is a 0.8 fWAR in 140 PA this year.
Why every conversation on catchers dissolves into how well they do one facet of the job (whether it be framing or batting) and not just using highly respected numbers that account for all sides of offense and defense in terms of identifying value is crazy. Contreras is a very bad defensive catcher, I would love to see him move to the OF but part of that is because the team would then be able to start Caratini more, a guy I think has the potential to be a 3-4 fWAR catcher in a league where those are quite rare. But if the Cubs didn't have Caratini, even with his deficiencies in terms of framing, I still think Contreras is a fairly quality starting C and you wouldn't replace him just to get a light hitting framer in the game because that guy is worth less than likely the position player Contreras replaces.
With regards to the trade and the hindsight, Kemp is a bigger need and necessary talent to the roster than Maldonado. Even in this worse case scenario where Contreras is out, would you rather have Kemp and Taylor Davis or Garcia and Maldonado?