No, I did not watch the video. I have read there is nothing there but the Titanic, and a sandy bottom. It has 4 days of oxygen, but it has never been tested. And worst of all, the trip usually takes 10 to 12 hours. 2.5 hours is the decent. It can resurface automatically, even if everyone is unconscious. This does not bode well. My guess would be they lost pressure.
I agree that they probably lost pressure. If the vessel had lost contact with the surface, there would in no way continue the trip. If at all possible, they would have immediately tried to return to the surface. Contact was lost enroute to the wreck. As far as I understand the timeline, they did not have time to reach the site. Thus, there simply is no other logical conclusion. The longshot hope is that the commo tether broke through collision or snag and they are somehow unable to ascend, but that is a hail Mary hope at best.
