Conspiranoia

Let's get the facts clear first.
Komiharu's slip-up couldn't have happened without the permission of the camera staff, director, editing staff and broadcasting department.
The director, for some reason, gave her free reins to so something so stupid, or even clued her in to it.
The camera staff kept filming something that anyone could easily see would wreck the program.
The editing staff went over this shit, clipped it together from different angles and sent it off to broadcasting.
Broadcasting green-lighted it for airing.
Then, management decided to try to pull it in later on, using quite some screentime to put Komiharu in a more positive light after the date episode.

Management didn't have any reason to snipe Komiharu's career - she wasn't unpopular enough that her career needed a fake scandal, and they even reeled it in later on.
This suggests that it was unintended by upper management, which would likely have intercepted it in an eyeblink if it had gotten past them. AKBINGO isn't run directly by management, so this of course makes sense.
It would be easy for the AKBINGO staff to slip the date special past management's eyes if the 48 Group works anything like a normal, multi-tiered corporation - AKBINGO would be on the bottom of the bottom, and not under direct supervision.

Now, who did it, and who had interest in sniping Komiharu's career?
It could have been a staff member, but it isn't likely. While we do know that some staff members are involved in the fandom and could thus come up with plans to sabotage the careers of the idols they didn't like, a plan such as this would have required the cooperation of multiple different departments, and that would take much more time, money and effort than one or two staff members could be expected to put in.
It could theoretically have been a fluke, but no. The episode passed past multiple departments without any kind of interference, and this is the 48 group. The group has a track record of spotting scandals from miles away, and when they do come out, they shush them down and attempt to avoid talking too much about it until things have settled down. This was too slipshod to be a mistake - with the standards we usually see, there's no way in Hell all these departments let an obvious scandal slip right through.
It could not have been management, as explained before. Management had no reason to snipe her - she wasn't so unpopular that she needed a scandal to get her back up, and she wasn't so popular that she needed to make space for other members. It's all made moot by the fact that management tried to clean it up by giving Komiharu more screentime and having her apologize for the things she did. The reaction was so fast by 48G standards that we have to assume it came from higher up.
It could have been the sponsors.
AKBINGO and multiple other AKB undertakings are sponsored by Softbank - a zainichi-founded, zainichi-owned company. Now, I do admit that not all zainichi Koreans are frothing right-wingers, but it makes sense if you'll read on a bit.
Komiharu is in roughly the same popularity bracket as Okada Nana (zainichi Korean - go Google it in Japanese if you're really in doubt) and recently, Kuramochi Asuka (infamous Koreaboo whose career has seen a bit more activity lately - a suspiciously convenient time for a potential rival to be eliminated).
All three have seen heavy pushing, but have now settled around the middle end of popularity - regular, though not all-consuming, TV appearances. Since they're not drama actresses or TV show hosts (Komiharu’s only TV role is in a small NHK edutainment show, something that’s far too small to have any real impact on her career), it means that all three of them are competing for screen time in one single thing - variety.
Now wouldn't it be convenient for the Korean national interest if Komiharu experienced a sudden setback on a variety show, freeing up space for a zainichi Korean idol and a shameless Koreaboo? Okada is there as more of an investment (remember, her parents are rich - the zainichi media clique isn't just my imagination, and you know that too). Kuramochi is more of a straightforward propagandist, there to shoehorn in segments about Korea and Korean claims to Japanese culture. Kuramochi is probably the most straightforward tool out of the two, but having Okada in there means placating her rich parents and thus building contact networks, as well as giving an ethnically Korean idol in the 48 group for people to get used to the (distinct) looks of, as well as allowing for a convenient reveal when the fanbase has been softened up.
Softbank has the motivation - destroy the career of a potential rival for two of Korea's most promising inroads into the 48 group.
They have the resources - bribing the camera staff, director, editing staff and broadcasting department for a single episode barely touches Softbank's pocket change.
They also couldn't have done anything else - Softbank is only a sponsor, not a co-owner. The fact that management tried to fix the scandal means that the order didn't come from above, which means that it wasn't Kyoraku (which harowota have been claiming is Korean-owned for a very long time, but even they haven't been able to find any proof). Since Softbank is only a sponsor, they would likely have been rejected if they'd come directly to management about pushing Okada and Kuramochi, and this would also have clued management in to their plans. Yasusu is distinctly Korea-skeptical since SDN48 crashed, as the Koreans weren't willing to share their market share, and he's even taunting them with letting mainland Chinese vote, as well as organizing more concerts in China and Indonesia. The recent Jakarta coverage was a slap in the face to the Koreans, and I don't think it's gone unnoticed.
I'm awaiting the sperging.