No, he's not missing anything. 50 getting shoved through his gap cut off his line of sight. He didn't get to the cutback because he didn't see it till it was too late.
I get some people think Bush is done, and maybe he is, but on that particular play, he was blocked out by a failure in front of him.
Cut off his line of sight?
If you've ever played hockey or football, I can tell you that no one sees 100% of the things that develop in front of them. There's swarms of bodies on most every play.
The difference between what you saw on that play and Bush in general and <insert all pro ILB name here> is anticipation and reading. Every LB has their lineman get blown up in front of them. The difference is Bush is a wuss who won't stick his nose in and attack downhill. He floats on nearly every play- I urge you to watch him.
The good LB's in this league STEP FORWARD when they see a running play develop. The first time you see Bush step forward in that vid is when it's too late and his gap integrity is already blown.
Be a different story if he read his keys, charged forward, and missed- it happens to everyone. I'd rather have someone be solid on their fundamentals and miss the tackle vs someone who blew their assignment AND missed the tackle.
The dude is flat out soft and hates contact. Just watch him.