There are external GPUs now that use thunderbolt, prior to this you could run external displays at a greater resolution than was available via HDMI at the time.

There are external GPUs now that use thunderbolt, prior to this you could run external displays at a greater resolution than was available via HDMI at the time. Firewire was mostly not used because people were content to endure USB, and USB had a larger availability on consumer hardware. Apple gained nothing by spending money to add the port to their computers so I find it hard to buy that they had a secret malevolent purpose in doing so. In this case they rolled the dice on a superior solution and it didn’t pay off.