The original was 30-pin, the new one is 8-pin. The reason this could happen is that many of the pins in the old dock connector are now legacy and no-longer use

The original was 30-pin, the new one is 8-pin. The reason this could happen is that many of the pins in the old dock connector are now legacy and no-longer used. Examples include a number of FireWire interfaces and some iPod-only S-Video and composite outputs. 8 pins were for FireWire alone. Also, the 30-pin's availability of dedicated ports for many functions let accessories connect directly to the inputs and outputs they needed without needing to go through a digital conversion process that would require additional software and require digital processing hardware. So an iPod dock could connect directly to the power and audio out ports, resulting in a simple and reliable circuit design. Now, years later, the cost of processing hardware has dropped massively so it's more feasible for a number of accessories to incorporate digital processing hardware to get the stuff they need from the digital in/out pins rather than needing dedicated pins.