Dean - The problem with the first GIF (in which Willies appears wide open to you) is that the throwing lane isn't completely open. I honestly think Hamilton's route was too deep and didn't clear the Mike out of the way in time, so he hasn't cleared the window. Beathard throws that ball with pace (as he would need to do), there's a chance the Mike gets a hand on it and tips it. If he anticipates to throw where Willies will be as soon as the Mike clears, there is a chance (as OK4P said) that Willies gets his lunch handed to him. I think you can see Beathard wants to hit Willies, but again, the window was muddy enough that he thought better to check down. I'd say if Hamilton doesn't arc so much around the DE to release into his route, that's a great opportunity to hit Willies on the dig.
Now, on the second GIF, the window is wide open and he throws Hillyer into it beautifully. There is no one underneath and the bracketing coverage can't get a read on where CJB is going with the ball, creating the void for Hillyer.