Short answer is that ESPN’s FPI model is updated with data from each game once it happens, which impacts their baseline assessments of each team’s relative ranking on Offense, Defense and Special Teams (which in combination informs the overall team FPI). Then they run enough simulations of each remaining game to produce statistically significant resutlts and create their predictions. (538 actually uses FPI for 75% of their model, while the Playoff Committee’s CFP [or AP if CFP not yet released] rankings make up the other 25%)
So it actually doesn’t have to do with who has conference games left (the model now knows that only we can win the South and that only UW/Wazzu can win the North, so the championship game iterations only consider two matchup possibilities)… what it means is that the net effect of our performance against Colorado (combined with the net effect of everyone else’s performances) exceeded our previous relative baselines enough to swing the projections of the remaining games in the new simulations (that are based on the updated baselines). For what it’s worth, last week FPI favored us over Wazzu in P12Champ scenario but not against UW. So our performance against Colorado was, on a relative basis, enough to “change” the model’s mind about our chances head to head with UW.
ESPN on how FPI works:
“The Football Power Index (FPI) is a measure of team strength that is meant to be the best predictor of a team’s performance going forward for the rest of the season. FPI represents how many points above or below average a team is. Projected results are based on 10,000 simulations of the rest of the season using FPI, results to date, and the remaining schedule. Ratings and projections update daily.”
538 on how their models work:
“Games are simulated mostly using ESPN’s Football Power Index. We say “mostly” because we’ve also found that giving a little weight to the playoff committee’s weekly rankings of the top 25 teams helps add to the predictions’ accuracy. (We use the Associated Press Top 25 poll as a proxy for the committee’s rankings until the first set of rankings is released in the second half of the season.) Specifically, the model’s game-by-game forecasts are based on a combination of FPI ratings and committee (or AP) rankings — 75 percent on FPI and 25 percent on the rankings.”
For math types so inclined, the detailed 538 explanation can be found here:
https://fivethirtyeight.com/methodology/how-our-college-football-playoff-predictions-work/
Utah @ 
Colorado .
