I think part of it is talent level, but another part is MC's system, philosophy, and scheme. Allen Lazard was a top-10, 4-5* WR recruit out of HS. Went to ISU, broke records, made 1st team All-Big 12, etc. Then what happened? He doesn't get drafted, signs as a UDFA, and lands on a practice squad. How's that happen? The guy had insane measurables, so instead of developing his other skills MC just figured we can throw it up his way and he'll outjump/outsize/outmuscle most Big 12 DBs. Good for ISU. Not good for AL. So when it came to route running, getting separation, footwork and mechanics, and other essential skills for a well-rounded WR, NFL clubs could see he was lacking. So his name doesn't get called on draft day. Then he gets into the League, gets a few years of good coaching focused on rounding out his skills set, and what happens? He's putting together a decent career as a pretty consistent contributor on a good NFL team.
I do think we'll see more ISU guys getting taken in the next year or two than they have seen in the last 5-10 years. Hopefully they're doing more to develop guys into the best overall players they can be instead of just figuring out how they can best use their existing skills to win games.