1) The user /u/ControlTheNarrative (CTN) made plenty of posts before losing the money where he made it very clear he knew exactly what he was doing. He had a post where he spelled out exactly how to gain the extra leverage and that his "personal risk tolerance" meant he could handle 25:1 leverage. Additionally, his response after the fact was something along the lines of "once I earn another $2000, I plan on doing this again". This kid didn't just click a wrong button and end up with the extra leverage, he was well aware of what he was doing.
2) Take this one with a major grain of salt, but based CTN's comments in the original posts and some comments by other users, it seems like this might not have been the first time CTN has used this exact trick to blow up an account. When the video was first posted, multiple commenters mentioned that he'd done it before and some of CTN's comments after the fact seem to hint at that. Again, take this with a huge grain of salt since I have nothing concrete to back that up.
The last time RH was in the news for some user losing way more money than they had (IR0NYMAN) I actually felt for the user a little bit and can understand why RH (supposedly) didn't go after the money after the fact. IR0NYMAN was creating box spreads, which can be a legitimate strategy, although they are very hard to find a situation where you can make money with them. That user stupidly didn't understand RH's rules around options exercise which is how he got screwed, but had he been able to hold all his contracts to exp (like European options allow) he actually would have been fine.
I can understand RH writing off IR0NYMAN's debt because it didn't seem like the user truly understood what he was doing, but this one feels different, IMO.