I guess you can develop hand/eye but I think a lot if it is just natural. I think the best hitters at every level just have that. You can build up strength and work on technique to get better but you still have to square it up consistently. I have to disagree with Quigs that luck has a component. Maybe for a few weeks or some time but great hitters are not lucky.
(whispers....) I was joking... my % don't actually = 100% on purpose. You know..a la the old Yogi Berra quote about "90% of baseball is mental...and the other half is physical."
The "luck" part that I refer to are the bloopers that drop in or the mishits that find a hole or a soft spot to die before a player can get to it. But, as they say, "It all evens out in the end." ...with line drives that get caught or the frozen rope thats snagged or the deep bomb that an OF sno-cones.