Intel was a major backer of USB (partly why it's so CPU intensive these days - it means Intel gets to sell more CPUs!)
USB 3 is handled mostly by the controller, which uses DMA to transfer the data in and out of main memory, so it's pretty light on the CPU. Thunderbolt is a little better, but only because it is basically a PCIe bus and thus a security nightmare. USB is a good compromise between performance and security.
USB C was something Apple gave the USB
Say what now? The design process had been started before Apple even announced Lightning, and they didn't share any technology. The USB-C connector is actually the opposite to the Lightning connector physically. Lightning has the connectors on the outside of a protruding jack, where as USB has the connectors on the inside. The USB design is superior - it's stronger, the metal shell of the socket guides everything in to prevent damage, it's self-cleaning and the contacts are protected from dust and grease from fingers. It follows previous USB designs that used the same principal.