I work in TV ratings. A few things probably go in to this.
1. Heisman Ceremony was the lowest rated in a decade...everyone knew who was winning and there was no warped personality (Manziel in 2012, Jameis in 2013) to promote. Weaker lead-in almost always equals weaker performance in live or live+same day viewing. Therefore that comparison to the last 2 years is not apples to apples.
2. DVR is more prevalent every single year, and that viewership won't be in for 2 weeks.
3. Didn't seem like people were as excited about this one nationally...probably felt to a lot of people like the same thing again, and why do that on a Saturday night?
The Heisman running long actually had a slightly positive effect on the overnights...in the finals that came out this morning we got bumped down to a 1.2 HH rating, which is what he was referencing.
HH is kind of a garbage measurement for a niche program like this on a cable network in my opinion, so I looked at Men 18-49 (target demo)...actually ranked 2nd on the night in that demo, just a tick below its lead-in. Which essentially means that, when put in context, ESPN is going to be very happy with its performance, even if it isn't as highly rated as the last few years were in a vacuum.
I would wait a few years if I were them to commission a U3 chronicling Al's signature win next year against an unranked Climpson, however (that's a joke, people).