It seems like William Contreras was the best centrepiece the A's could get, but they didn't want him because they have a couple of catchers in the pipeline.
So they called around.
Esteury Ruiz is really the lynchpin of the entire trade. I think he's a s***** slap hitter. But he's super divisive. There are people who think he is a blue chip prospect.
Ruiz is the Kevin Smith / Brett Lawrie of this deal for Oakland; the major league ready position player who they think can be a two way difference maker. Both of the Chapman and Donaldson trades flopped for Oakland largely on the failings of Lawrie and Smith (Hoglund could still salvage the Chapman deal...)
If Ruiz flops, this Murphy trade will probably be awful in hindsight. Obviously the A's also got three live arms, but they all have some warts. Maybe one of the arms turns into a mid rotation SP or a bullpen stud and then the thing looks okay in three years even if Ruiz is replacement level.