I think you could say this was a stupid trade for Atlanta too. They traded away the better catcher plus 4 other players (though it didn't look like much was there).
Murphy had 7.7 WAR vs Contreras' 12.6 in the last three years. Murphy is three years older, and more expensive.
For Oakland, this was a complete disaster. Only one player of the five they received remains with the club and he is struggling in the minors (Royber Salinas). Kyle Muller, Manny Pina, Esteury Ruiz, and Freddy Tarnok all played MLB games for Oakland for a sum total of -1.1 WAR.
Seriously, Rachel Phelps would be proud!