I could write an essay about this, but this is the super condensed version. It's a bad QB situation with Speight injured/regressing, JOK is bad, none of Hoke's guys panned out (Malzone, Morris), and both of Harbaugh's QB's are apparently some combination of not being physically/mentally ready to play yet (true freshman and RS freshman, Gentry is now a TE).

Additionally, our situation at tackle is fucked. The coaches screwed up with recruiting and basically lost two tackles late in the recruiting process in Harbaugh's first full class, and they never replaced them. So now we have no RS freshman tackles available when we should have had two. Newsome being out for two years with an injury made this situation even worse.

All of this stuff is on the coaches because they screwed up the recruiting of the tackles and who they got as a QB grad transfer (O'Korn, although the Rudock experiment worked out quite well). In a perfect world one of Hoke's QB's would be decent and a couple more of his OL would have panned out. That obviously didn't happen.

All of this is compounded by the coaching staff calling plays that don't work for bad QB's like we currently have. I'm not sure if you watched the Indiana game today, but the announcers pointed out multiple throws where Michigan had wide open guys and JOK never saw them. It feels like the coaching staff is basically satisfied with the play calling since guys are getting open to some degree, but again it doesn't matter if JOK can't look past his first read.

Even with all that, the coaching staff has to do a better job at the end of the day. We are not the only school in the country with OL problems and a bad QB.