If you need them explained, it may never sink it, but it's worth a shot so you can live in peace.
Just a few would include:
-More favorable schedule
-The team as a whole is now a year into this new system
-More experienced OL with time under their belts and an off season to really work hard. Earning praise from the coaches, something that didn't really happen last year.
-A Junior Hill and Jamaal. One year older, that speaks for itself. Jamaal is bigger, faster, stronger, and smarter. Hill is one year removed from rehab and has had all the time in the world to get help on his mechanics.
-A much deeper WR corps. I'll take a healthy corps (including TEs) of 9 or so good players than Hoffman + injuries = maybe one or two more dependable/consistent guys.
-No walk-ons starting in the secondary and a deeper, more experienced secondary.
-Anae is believed to be comfortable in the system now and should open the game up a bit more and get more creative.
-We'll easily have a better passing game and better running game for reasons stated above.

I dunno, there's a few. If you can't see the "how" of these, I don't know what to say.