Todd Graham (Pitt, ASU, now Hawaii head coach) voted Irish 9th....had cincy 5th Indiana 6th

They vote on primarily on self-interest to the extent they can get away with it.

There are a number of coaches who have voted up their own conferences, and their next opponents, because it made them look good. Spurrier (and there are plenty of others who were guilty including Holtz) was notoriously famous for this. When he got called on this for a particularly egregious vote, off the top of my head it was a sub .500 team he was playing next that he voted in his top ten, he blamed an assistant who voted for him because he was particularly busy that week.

Once they decided to publicize the actual votes, a lot of the worst skullduggery stopped. It also doesn't really matter much anymore since the folks who do the final 4 picking don't pay much attention to the coach's poll anymore since they have the metric polls when they need them.