I suspect it would be to prevent information about his crimes from coming out.
Hillary probably has lots of dirt on Obama and his very real treason in giving away our money and secrets to muslim nations and militias.
Obama correspondingly has dirt on Hillary about her corruption and stealing money through her "foundation".
A match made in hell.
I wonder why Obama delayed the release of his book. Does he need to make some revisions?
benghazi, Ghadaffi, Muslim Brotherhood, fast and furious, uranium to russia, fake dossier, false FISA warrant application to name a few.