Actually watching the Niners game GB had a man on the runner almost everytime and usually behind the line of scrimmage. They simply could not tackle well. Re watch the game and you will see an endless stream of missed first tackles. There was no one else there after that with the Packers in that 4-3 zone base with the linebackers 5 yards off the line.
You know I always take that challenge. The whole game isn't available yet but I did rewatch the highlight package:
There's one single play where a Packer gets a single hand (while being blocked) on a 49er in the backfield. Every other play in the highlights the Niner back is 8 yards downfield before contact. Watch the position of the linebackers at 49 seconds of the 2nd and 4:48 of the third in particular. They're 8-10 yards off the line of scrimmage.
That's one strategy to beat Zone Run, you put the linebackers so far back that they can evade the blocks coming from the lineman releasing on their double teams. If that was the plan, it was clear by the 2nd quarter it was a huge fail.
To beat Zone Run you must prevent the O-line from getting their initial double teams. If they are forced to lock up 1 on 1 then it eliminates the peel back blocks and the release to the second level blocks. Watch the KC-TN highlights for how the Chiefs handled Henry. In running situations they were in the 46 defense or variations of the 46 all the time.
Since we're way down in the weeds here I thought I'd put up a couple links to explain what the hell it is we're talking about here: