I would think that the optimism comes from the fact that all those guys come back and have had the entire off-season to fine tune their mistakes and continue to get better. There wasn't a complete overhaul with new guys coming in, which I think would have been more concerning than everyone coming back. There were some games where our O-line did a very good job, and I think having Purdy back there with his mobility helped with him taking hits / sacks.
Returning all of the guys from an OL that was 5x worse than Iowa's isnt a good thing, IMO.