Why? Whatever had happened to Lekhraj Kirpalani, he was suffering from a kind of mental illness or psychic disorder. He was suffering from a quite typical egomania ... he was suffering delusions of grandeur.
He thought he was God and everyone who did not rush to and worship him (from the Europeans powers and Gandhi downwards), or criticised him, were insulted using extreme exaggerations. Those closest to him were equally crazy to believe it all. They had lost their mental equilibrium and their inflated egos were engaged. Lekhraj Kirpalani tended painted everything in grandiose, simplistic opposites using the only metaphors he and the girls knew ... those from Vallabhacharyan Bhakti stories.
The Brahma Kumaris took his mental illness and turned it into a religion where kept failing but spread like a virus to other people to a lesser or greater extent. 75 years later we are still trying to unpick the delusional aspects of it and, as it keeps failing, the Brahma Kumaris keep trying to patch it up and keep it inflated by adding and changing it.
Delusions of grandeur is a subtype of delusional disorder (GD) that can occur as a wide range of mental illness, including in two thirds of those in manic state of bipolar disorder, half those with schizophrenia and a substantial portion of those with substance abuse disorders. It is characterized by fantastical beliefs that one is famous, omnipotent, wealthy, or otherwise very powerful. The delusions are generally fantastic and typically have a supernatural, science-fictional, or religious theme. There is a relative lack of research into GD and about 10% of healthy people experience grandiose thoughts but do not meet full criteria for a diagnosis of GD. Grandiose delusions are distinct from grandiosity, in that the sufferer does not have insight into his loss of touch with reality