For the same reason some thought that Manuel was going to be a good QB when he was drafted. The same reason Marrone was going to be a great HC when he was hired. The same reason Gailey, Jerrahs "biggest mistake firing him", was the diamond in the rough that everyone else missed. The same reason WannaStache was exactly the DC the team needed. And so on, and so on.
There was no reason to believe any of those at the beginning, but some choose to anyway. They are the name you have chosen for this board.