Someone, I think it's the Illuminati, threatened the Dalai Lama with something, which I can only make intelligent guesses as to what it is.
The Dalai Lama had/was given two options:
Option 1: Unknown, but definitely worse than option 2
Option 2: Create schism & sufferings that follows
He can't create schism with common protectors, as other sects & religions are also worshipping them. Therefore, He did it with Dorje Shugden, the uncommon protector. The real issue was never who or what Dorje Shugden is.