According to this https://www.cultofmac.com/790897/today-in-apple-history-ligh... it was supposed to be USB 3.0 but there was only one device that utilized USB3.0 speeds:

"Apple’s connector supported USB 3.0 host, but the only accessory that fully supported this feature was the camera adapter that includes a USB-A port. Most Lightning cables to this day support only USB 2.0, with a maximum data transfer speed of 60MBps."

I seem to recall when lightning was announced, someone (probably Steve) said it was faster than the 30 pin. Then again Steve was known to blow smoke of products (remember, FaceTime was open source according to Steve when announced).