I think it was because he was going to spill the beans on the Iran deal. The Iran money paid was not necessarily paid to Iran, but my have been going to cabal leaders, laundered through Iran.  This is just my thinking based on what Ronald Bernard reported. If you haven't seen, (or rather read) this interview, it's very eyeopening.  https://youtu.be/nEpcY5JU120  Also see here:  The Reason Why Barack Obama Targeted Michael Flynn Goes Well Past Petty Politics And here various CTH Articles