noticed several 4 stars being recruited by neb but with very few other offers from high major programs. are these kids with grade issues?
why would a 4 star recruit only have offers from UCF, cincinnati, louisville, etc
In generall there are multiple reasons this can happen and it differs case by case. Some of the reasons (from what I've gathered) can be:
1a) A kid has a hole in his game. I actually think the guys who do the rankings do a decent job but the coaches simply are better. We are talking about kids who are so much more athletic than 90% of the other players on the field that the warts might only show up on a handful of plays...warts that will show up big time once he's on a field full of high D1 talent...and they are things that only a real pro can see.
1b) the coaches think a kid has reached his (physical) potential and will fall to the wayside as other kids continue to get bigger, stronger, faster, etc.
2) with that said the coaches can be wrong too and maybe the recruiting rankings saw something (maybe at a combine coaches couldn't attend) the coaches missed...though the first two reasons tend to be more common than this one
3) recruiting is a two way street. There aren't that many "can't miss" prospects each year. After those a lot of programs tend to bucket prospects into tiers. Kids need to get film out, go on visits, respond to communications, etc. Not every kid knows how to navigate the recruiting process. It is not unheard of to have a kid passed on simply because schools are getting enough interest from other kids they feel are similar and don't want to spend all their energy chasing down a kid they dont feel is "can't miss." Its creates the perfect opportunity for schools like UCF and Cincy to swoop in and make them a priority.
4) as you mentioned grades could be an issue...as could other off field issues...but it can also be an intangible such as a kid not showing a passion for the game...coaching staffs often talk to people at the kids school before offering and simply decide it's not worth the effort. It's not that smaller programs ignore the warning signs...it's more that they don't have the luxury of moving onto the next 4*.
5) There are also the misc. odd reasons that tend to not get publicized during a recruitment. My school once landed a top 100 kid who had a couple offers from local schools (in the south) and one random offer from a northern school (my school). In all, there were a couple of big name offers but you'd expect a kid ranked as high as him to have significantly more...especially one who took his recruitment past his senior season. We later found out why...he had a speech impediment, was embarrassed of it and thus refused to talk on the phone. Coaches would call a few times and then give up. My school figured this out and decided to email him instead.
There are other reasons as well but my point is that you have to look at it on a case by case basis.