He's trying, in the hearings, to not let it look this way, but the truth is that he and Exxon Mobile stand to benefit a great deal from a Tillerson SOC. Also, Russia will benefit a great deal.
Putting it a slightly different way, Tillerson's appointment makes the most sense of you replace "Trump" with "Putin" in sentences that refer to who the leader of the United States is.
The composite graphic above explains this. The context for those graphics is here: