This was a very educational book and clarified some of the disturbing trends about how the Obama administration mishandled the war on terrorism.
There's a lot of "how" spelled out and no speculation or information on "why," but the author didn't claim any insight about the motivations or reasons for the upper level administrators for taking the steps they did in responding to the external threats to the US.
However, if you want to know why, after 7 years of George W Bush faithfully keeping terrorist attacks out of the US, we suddenly started experiencing methodical and regular terrorist attacks in the US under Obama, this book will spell it all out for you.