Frost, Crouch and Frazier were given very safe and limited passing games to exploit on Husker teams that were notorious for the run, so defenses bit on almost every play action pass. Those run-heavy Husker teams also managed to recruit solid receivers, along with epic offensive lines that bought the QB lots of time. Even given the most favorable and low-pressure passing situations, those guys were 50% passers. They avoided crossing-patterns, fades and touch passes. They almost never improvised: there was a primary receiver and that's where they threw it, whether he was covered or the secondary receiver was suddenly wide open. Lots of super safe screens. Scott Frost had a hard time hitting receivers in stride and a lot of his completions were at the feet. Crouch just wasn't a good passer at all, even if his motion was prettier. Frazier seemed able to turn it on better when needed, but you would never watch his first two seasons and say he was a better passer than Martinez, and he spent his last two seasons overseeing a juggernaut. We remember those guys winning, not all the passes they blew.
Agree that stats are deceptive. Otherwise we'd be hailing our greatest running quarterback ever, Jamal Lord. I just think it's easier for some folks to focus on Taylor Martinez's arm when the team has a bunch of problems even Peyton Manning couldn't cure.