Here is an in-depth interview on how Scott McCloughan thinks, from last season:
"B/R: You've obviously made a huge decision to keep Kirk Cousins on the franchise tag.
SM: We did the franchise tag, and I know everybody made fun of me, and that's fine. But you know what? The guy won the division. They won nine games. They won four games the year before and turned around and won nine, and he plays all 17 with the playoffs, and we went on the road at the end of the season having to win, and we beat Philly and Dallas, both at their places. You know, the NFC East, I don't care if they're good teams or bad teams, you still don't win on the road. We didn't early in the season, but he kept going and going, and the players rallied around him.
B/R: You also had very little choice. If you don't franchise him, other teams bid. At the same time, it's hard to pay a quarterback the market rate after only one full season. If you give Cousins $55 million or $60 million guaranteed, you get criticized even more.
SM: I told Kirk when he came in—and his wife must have hugged me for 10 minutes because he just went from making $600,000 to $19.9 million—I told him, "You take care of me and this organization, we're going to take care of you. I promise. And we're going to build this roster to where you can be average and still be good. I promise you."
Scot McCloughan Q&A: The Philosophy and Tools of a Successful NFL GM | Bleacher Report