What we CAN know is that he sneaked in and didn't make a big production of it, carrying a king-size Bible and waving to the cameras.
So he acknowledges that he is not the most important one here. Perhaps it is just modesty, perhaps a nod to the proprieties, perhaps a recognition of his Lord.
But whichever, it's a good sign that the man has some humility.
Do not disagree...
He knew he didn’t have to make a big scene about it. He realized he would be sitting among other congregants, and his attendance would be known, by word and photograph.
When I was places where the preseident-elect was coming, if the didn’t want pictures, the Secret Service had methods of assuring that.