Probably based on their own "FPI", which has underrated us all season...
What metric are they using? Is it purely wins and losses and not who these teams have beaten?
...at least compared to the other polls.
Either way, ESPN seems to have our CFP competitors (OSU, TCU, Baylor) with bad SOS' too, so that ours is still more difficult.
Here is ESPN's "playoff picture" with their other categories.
http://espn.go.com/college-football/playoffPicture
Notable is their "Game Control" stat. We were #1 for many weeks until we lost to Bama. Now they are #1 and we are #2. Why does this matter? In the interview after naming the playoff teams last week (keeping us in at #4 after we lost at Bama), the chairman of the playoff committee used the exact words "game control" to talk about the teams that deserve to be in it.