You may be confusing audio and video. Unlike USB-C the Lightning connector has such risible bandwidth it cannot carry a full video signal. Apple's Lightning to HDMI connector actually has a full computer inside the dongle that decodes the compress (MPEG-2, H.264, H.265) video sent over Lightning to uncompressed HDM video.
http://www.iphonehacks.com/2013/03/why-lightning-digital-av-adapter-cant-stream-raw-hdmi.html
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