At its simplest, strikes are the result of appropriate deflection of the ball as it hits the pins. Too much deflection or too little deflection will create the wrong angles for the pins to deflect into each other. In these cases, the solution is to find a way to change your ball reaction to create more optimal deflection through the pins.
Too much deflection often results in flat 10 pins and “weak” splits, such as the 8/10 (for righthanders). Here, bowlers need to create less deflection by going to a ball that retains energy longer, increasing their axis rotation angle, and generally delaying the ball’s hook.
Too little deflection will often result in 9 pins or ringing 10 pins. To create more deflection, try to get the ball to roll a bit sooner and/or skid a bit less by using more forward roll or more surface, or by switching to a less angular bowling ball.