If there is a will then there is a way to do it at a more sensible time.
1) People need to rest, exhibiting at a show like this is NOT A HOLIDAY. They also need to focus on their own booth to make sure it's all ready to go the next day. It's possible that they have to pack/unpack and move everything before and after every showday and can't just leave it out over night.
2) Agreed: It doesn't have to be done on the CES location, or at the CES time.
3) Pimax probably sent the exact amount of people to CES as they need to run the booth, if they didn't need one, they wouldn't have sent that one at all (also, the staff on the floor are probably marketing/support staff).
4) Hauling around their HMDs and demo computers (which are probably supposed to be locked up) to random places and installing experimental drivers and stuff on them is probably one of the last things they would want to do in their little free time after the show every day. Their demo setups are not something they want to mess around with, they need it working the next day.
5) They would need permission from higher-ups to do this, time-differences make this annoying and slow, and there is already so much else to do.
6) Other stuff that takes too long to type up and gets more and more speculative... I don't want to argue anyway, there's literally no use, what's done, is done (or; what isn't, isn't).
Yes, they could have jumped all of these hurdles and others, if they really wanted to. But why? Why not just do it at a more opportune time? I mean it sure seems like they didn't do all that stuff, so I guess history is in my favour?
Also one more thing, the 'greatness' of this opportunity is debatable to say the least, in my opinion it would have been a bad opportunity, or 'a good opportunity to do a thing badly'.
A 'great' opportunity, to me, would mean when both companies have an established interest in working with the other, have been in contact and are free and ready to continue to the next steps. Probably some time AFTER Pimax have solved most of the quirks of their own HMD and probably not during a big milestone like a huge consumer exhibition (I don't even know the state of the TPCast thing, maybe they still have some things to iron out too).