Why? He was a first-round guy coming into the year who fell to the second. Sox know him from their Area Code team. Possibly they took him a few picks before some other teams would have, but he certainly wasn't expected to be a third rounder.
Eloy got a hit, which is nice, but 112 mph with a 9 degree launch angle. If he doesn't start hitting the ball in the air, he's going to be out of the league within 2 years.