In modern college football, with the speed / athleticism on defense, it is difficult for QB's to make it through the season upright.
Shrader is a proven commodity [flaws and all], but there is a dropoff on paper when we move down the list with all of the other candidates. Lamson -- size and experience. Villari -- unproven / productivity. Morgan -- upside. Etc.
Now, Lamson is hurt. And I'm guessing that the coaches are not confident about having to turn to the others [and for the record, that doesn't mean that Villari / Morgan CAN'T develop into something, just that maybe they aren't there now].
This kid gives us a high-major talent. He can come in and compete with the incumbent, he'll play some given that Anae / Beck use multiple QBs as part of the overall gameplan anyway, and if Shrader gets nicked up, Del Rio Wilson gives us a viable replacement option.
Now, how well does he throw? How quickly will he assimilate the playbook? How does he play when the lights come on and the pass rush is live? All TBD.