According to Faranak Margolese (“Off the Derech”) it is mainly because of religious figures who behave negatively”
False. I read the book – her conclusion is essentially that
people go off the derech when their needs are not met within the
community. Once people fall below certain levels of belief, happiness, and familial/communal connection (they vary by individual), it is virtually certain that they will go off.
Something like that, anyway – I recommend reading the book.
(There was such an element, but it wasn’t about religious
figures – it was the general population, if I remember correctly.
It was not given as a primary factor, though.)