What other conclusion fits? He made the single lowest-effort, least thoughtful play in MLB history; do we generally think of people giving low effort and little thought to a task as invested, or as just going through the motions (or put another way, just there to get paid).
Imagine this scenario; you ask a friend to come help you re-paint your bedroom, and let them know you'll take them out for dinner afterwards as a thank you. When they show up, they don't follow your instructions on what color paint to use on the accent wall, haphazardly use the paint roller, spilling paint on your window sill, and then lean up against a wall before it's fully dry. They then ask you where you're planning on bringing them for dinner. Would you infer your friend actually wanted to help you, or that they were simply there for the free meal?
I also don't think this is an attack on his character or integrity--as I said in my previous post, if he had only done one thing wrong on that play, no one would care. The fact he did FOUR wrong things, none of them truly physical (that is, he didn't dive to catch a ball and miss it, or drop an easy pop fly. The physical mistakes he made were only made because he was not giving sufficient effort), makes it very clear that, at least on that play, he was uninterested in playing baseball. If he has something distracting him in his personal life, that's perfectly excusable, but only if he surfaces that so his manager can give him the day off. He chose to be on that field, and if he is not willing or capable of providing even desultory effort, then he is by definition only there for the paycheck.