Simply put, VR headsets (displays mounted in such a way as to be placed in front of a person's eyes) have been visualized and built for decades.
Sure, but that's not what's being patented here. What's being patented here is a frame that you can slot an existing mobile device into to be used as a headset, where the headset detects the insertion and notifies the phone to switch to VR mode. That's not something that has been built for decades.
Lawnmower Man anyone?
Lawnmower Man didn't include a device like this. This is not a patent on any and all VR displays, it's a patent on a specific type of frame for mobile devices.