1. Preseason rankings include recruiting rankings that weighs a team which then goes to strength of schedule. Depending on the value, and we don't know because the formula is not known exactly, It's quite possible that this is disproportionate. It may not be on purpose, but considering that the current Big 12 teams are never going to be in the top 15 in recruiting rankings very often.
2. If you read down in the thread, bamacoug In responding to someone who brings up the recruiting part, says that ESPN removes that toward the end of the season, but with how little the rankings move at that point, that strength of schedule that was partially based on recruiting rankings is baked into the cake