I'm obviously not a recruiting guru either, but I think there are a lot of things that go into it.
1) I think the talent gap between the best and "least best" players is way bigger in basketball than football and there aren't near as many to go around. Most elite BB players play hundreds of games a year between the AAU grind and high school. They have the best coaching available at that level and a whole bunch of them come into college NBA-ready and their one year of NCAA ball is just a formality. No college freshman is ready to even think about pro football.
2) For all of his perceived faults (which are some of my perceptions as well), Kirk Ferentz is really really good at designing a program that does the most with his available talent and he hires really good assistants. Even though he was apparently a raging douche bag, there was no one better in the strength biz than Chris Doyle. That's a huge part of it as well.
3) In the past 20 years we've missed the postseason (bowl games) twice. Yes, it's way easier to make a bowl game than the NCAA tournament, but it's still a mark of success that recruits look at.
4) Iowa football puts a metric shit ton of players in the NFL at a lot of different positions, and has for a really long time. We put way more guys in than our record would indicate. Ferentz has the (earned) luxury of bringing a recruit in and showing him wall after wall of All-Americans and guys in NFL uniforms with Super Bowl rings. In the last 20 years there's only been one guy who played a full NBA season's worth of games in his entire career and he got drafted....20 years ago.
5) Iowa's football facilities are ridiculous for not being a blue blood.
6) Just flat out more success. If you're successful you're just plain going to get better recruits. Similar to how I've said you either have to luck into a unicorn coach or cheat, Iowa did a form of that when they hired Hayden Fry and they were smart enough to make his replacement a guy who worked for him. People like to use that as an argument for playing musical coaches but for every HF there are 100 Mike Riley's out there. And let's not pretend that Fry wasn't luck. He didn't have any big time experience, and that hire was a Hail Mary last ditch to save a 30 year turd of a program. No one knew how it'd turn out. Iowa basketball isn't bad enough to warrant another roll of the dice, especially when the odds are so terrible. People who want a new coach are the same type of folks who buy more scratch tickets so they can make up their losses.