They have to do the same thing that TCU has to do -- play a harder non-conference schedule. Unfortunately for BSU, their conference schedule is so weak (even weaker than the MW schedule which at least included BYU and Utah) that every week that goes by drops BSU in the computer rankings.
The last team to beat them was an interdivision rival.
I would agree with you, but they beat two ranked teams outside of their own division. They’ve clearly demonstrated that the BCS teams are inferior, which is why I have them ranked at number 1 and TCU at 2.
When the BCS finally manages to defeat them, I’ll change my mind, but until then, I don’t understand why people reflexively rank weaker BCS teams ahead of them.