Does this mean they underpowered the iPad 1 or overpowered the so-called iPad 2?
Are you being wilfully obtuse or is this something you have to work at?
This is pretty simple - the A5 has the latest PowerVR GPU, with what is assumed to be two cores. It's undoubtedly the best available, and the Sony NGP will be using the four-core variant of the same thing.
If you plug a better GPU into a screen that's driving the same number of pixels as previously, you gain a great deal of headroom in terms of what you can display.
Nothing's 'underpowered' or 'overpowered' here, it's just what happens when new technology arrives and becomes available in quantities that it can be integrated into devices.