Well, typically a pocket split is caused by a ball deflecting too much off of the pins. This ball deflection is caused by a number of things. If the ball is moving quite slow, it will loose energy faster as it rolls down the lane. Less energy means less hit on the pins. If the ball is lightweight, say 11# or less, maybe eve 12#, They start putting cores in the 13# balls sometimes, if they are generic cores though. The actual core shapes, since they are so heavy, can only be put into balls weighing 14, 15, or 16 lbs. The lighter the ball the easier it is for the ball to kick off the pins. The whole deck of 10 pins weighs close to 40 lbs whereas even the heaviest of balls only has 16. If you are using a 10# ball you're hitting the pins with about a fourth of their weight. Imagine a school yard fight with those odds...
also, if the ball hooks late and hits too far back on the head pin the pins will kick out differently due to both light and heavy shots. Too much through the nose leaves nasty splits, and too much on the 3, for right handers and 2 for the leftys, and you also get weak leaves.
If the ball is revving very little, like a straight ball, there is a much higher chance that the ball will not drive through the deck at the proper entry angle and will bounce upon hitting the pins rather than following the angle through.
Finally, if the ball rolls out and ends up hitting flat, means the ball looses a lot, most, of its energy down the lane, it won't have the necessary hook power to pull through the rack and will again kick off the pins.
To stop this problem, it is a solution of each issue. Use a heavy enough ball, get enough speed down to avoid early hooking, shoot a line that will avoid hitting high or low in the pocket, avoid rolling out when on too dry a surface by playing through the oil remaining in the heads, and don't try to force revolutions since it often kills them instead. (Also, revving isn't everything so don't be overly concerned if you can't get it spinning like tommy jones)
You haven't hit the pocket well enough until you've Wrecked the Rack!
I'm an English major, "if my doctor told me I had only 6 minutes to live I wouldn't brood. I'd type a little faster."