Apple for long tried to license display tech from Beijing university, a solid state microled chip with microlenses, but they never agreed on lump sump payment Apple wanted, despite it being "n-times the price" of their whole IP trading business.
So, it became a blocker, with relationship souring, and them resorting to "patenting around," poaching their engineers, and other nasties.
They tried to recreate the chip by themselves, but Beijing uni got a tip of it, and claimed that Apple is now "IP tainted" by what they saw under NDA, and them hiring their engineers.
And so, Apple went on developing "ordinary" transparent VR glasses instead.
A company called Kura is said now to reuse the same chip from Beijing university IC company in their own take on what Apple tried originally.