There have been innumerable books and articles on the causes of the current literal insanity. But The underlying cause is simply Atheism.
To explain a little, the cause is atheism - de facto atheism and its consequences.
De facto, because nearly all 'religious' people nowadays are Not; are actually materialists, even in their religion.
And the consequence is that most religious people are as bad atheists as the explicit, strident variety.
Atheism is a Spiritual state, more than a belief. It is very difficult and unusual Not to be a spiritual atheist... To think and live on the basis that there is No God, and that this world and life are Not an ongoing creation.
And That is The problem we should be working on...