For a lot of these guys, their job is to make these predictions throughout the process. If they came on everyday saying "I don't know" it may help their credibility, but it would destroy their ratings.
I don't think most of It was that outlandish. It seems to be the general consensus that Cassel came in as the presumptive veteran starter and TT impressed from the get go as Rex's hand-picked hope, and that EJ struggled through most of camp and then came on strong toward the end.
Whether the FO wanted to keep a veteran with a high floor for security or save cap space and go with lower floor, higher ceiling options was anyone's guess. It's unfair to, with the benefit of hindsight, trash them for not being clairvoyant.