It's Michigan's second drive of the day. After a a two-yard gain on first down, Michigan comes down in an ace formation with Thomas Rawls in the backfield and split tight ends. Minnesota comes out in man coverage with the safeties assigned to Michigan's tight ends and the corners covering Michigan's receivers on an island.
As the ball is snapped, Michigan's offensive line begins zone blocking to the left, which AJ Williams releases on a drag route across the formation (highlighted). But look at Elliott Mealer and Ricky Barnum: neither one of them are blocking the Minnesota defensive tackle covering them. Also Mike Kwiatkowski (TE on the top of the screen) is supposed to chip block the Minnesota defensive end but you'll see in a minute that he totally whiffs.
You can see Kwiatkowski looking back at the defensive end he was supposed to block. This becomes problematic later. The other problem is that the Minnesota defensive tackle has now engaged Mealer (highlighted)...
...and absolutely trucks him. Meanwhile, Patrick Omameh isn't blocking anyone, the other Minnesota defensive tackle has gotten inside Michael Schofield, and the playside defensive end has recognized the bootleg.
Gardner's two options here are Williams and Kwiatkowski, both of whom are breaking to the sideline and open. I'm torn because I'm not sure if Gardner has time to set his feet here and throw quickly (the video is more revealing), but he decides to bounce outside the defensive end.
As Gardner bounces outside, the Gopher outside linebacker (arrow) has recognized Williams running behind him and starts to recover after being caught out of position.
Gardner gets outside the first defender but has another one bearing down on him.
And throws the ball without setting his feet.
So Gardner shouldn't have thrown this pass, but this was his first career start and he's bound to make a few mistakes.
The real takeaway here is that I've never seen an offensive linemen getting trucked that badly. The interior of Michigan's offensive line is unable to identify who they're supposed to be blocking, and Mealer gets the worst of it. The defensive tackle that eventually plants Mealer is to his left before the snap, so I can't understand why he doesn't engage the defender. Meal et had a really bad game against Minnesota and this just adds insult to injury.