I'm an Iowa State alum/fan. A lot of the offense ran through David Montgomery or at least the threat of him because he could both run and catch in the back field. There were very, very good WR on the team (like Hakeem Butler currently on the Cardinals) which was of course opened up because of Montgomery. The last 2 seasons were marked by 1.5 seasons of mediocre at best QBs (one who was a 3rd stringer who surprisingly beat Oklahoma) and while there were good WRs, they weren't as much of a threat to defenses in their scouting report because the QBs weren't that good. The only true WR threat was Hakeem Butler. That is until halfway through the last season a freshman who was recruited by Alabama started to play and finished the season 7-2 for ISU and opened up the passing game way more.
Needless to say, Montgomery was a major part of every single team's scouting report as he was known for being such a good RB that could both run and catch, even after a better QB started playing.
If you objectively watch a lot of game footage, you'll see that the defenses routinely got past ISU's offensive line and it's well known the OL sucked, especially last season. The fact that Montgomery was able to do what he did is a testament to him. The OL rarely actually helped him. If he was not good at balance, breaking tackles, etc there's no way he would have left early let alone be drafted. He does not have breakaway speed, but can get good yardage. The guy is a workhorse who works his ass off so rest assured, I guarantee he's working on getting faster. He worked out so much at the ISU practice facility, even at early morning hours alone, that the ISU staff literally tried to lock him out of the building and he still got in.
https://www.stack.com/a/why-david-montgomery-runs-so-hard