Prefacing this by saying I am not trying to compare Iowa State and Iowa in terms of NFL. However...
Factories come in all sizes. There's the New Hollands of the world which make tractors and then there's the John Deere's of the world which make more tractors.
Iowa = New Hollands (respectable factory that doesn't put out eyepopping numbers)
OSU, Bama and LSU are more like the John Deere's of the world.
Try not to confuse the two by your use of "proven" because
Iowa is not in the top 25 historically in number of NFL players (fewer than Purdue)
Iowa is right in the wheelhouse of Rutgers as it relates to current number of NFL players.
Iowa has the same number of NFL HOF members as Lousiana Tech.
Iowa has fewer Pro-Bowl appearances than Syracuse
https://www.pro-football-reference.com/schools/
Iowa makes nice tractors but everyone wants a Deere, just saying