Hard to tell. Coaches do what they can with the talent they get. Bo has been consistent with his record, and tends to have a few games a year when the players just don't compete like they do the rest of the year. This isn't a rare thing for Bo or any other coach; you rarely see a football team that doesn't get tripped up once in an entire season, and those are usually done by outstanding top-5 coaches.
Is Bo a top 5 coach? Not right now, but he's keeping Nebraska competitive and learning, getting personnel around him he likes while also recruiting to try and handle a brand new conference. Okie State just lost to Iowa State yesterday... does that make their coach suck? No, it just means they had a bad week, and it happens.
I think you can blame either one and be correct, but you're talking about a grown man in his 40's trying to motivate and coach a bunch of college kids that want to drink and party just as much as they want to play football probably. Getting 19-23 year old students to concentrate for an entire year is clearly tough, otherwise you'd see every football team with 9 win seasons.
Bo's a young coach in the grand scheme of thing... coaches that consistently succeed tend to have decades of experience and be in their 50's or 60's. I can't get mad at college kids that have an off week, though I can get mad if a coach calls a bad game, or leaves his players unprepared too many times a season. Bo's doing fine, so are the players. This is an off season, and transitional season both with the offense and with Bo changing the defensive scheme to play against Big 10 teams.
You can be disappointed in the season, even pissed off, but don't go calling for the heads of staff when you're still getting 9 and 10 win seasons.