If this last video was real, she would appear to be in good enough condition to have sat for a real picture. So why did they release the photo-shopped picture? Why did they release the video of someone who clearly wasn't her? People familiar with AI have pointed out numerous anomalies that suggest it was an AI-generated deepfake video.
I agree that she's likely either dead or seriously incapacitated. So, the prevailing theory is that William was enraged over finding out that she had been having an affair with Thomas Kingston and either severely injured or killed her. Kingston either killed himself (official story) or else was Arkancided in the days before March 1. Timing of this seems highly suspect. Either he was distraught about Kate's condition or else was silenced, since he knew too much about what had happened.
There have been other strange goings on, such as some horses riding out in a manner to suggest a death in the royal family, a flag pulled down to half mast, with the media being told of an impending announcement from the royal family, only for a few hours later for the flag to be put back up to full and the announcement cancelled.
There's definitely something more than their having delayed an announcement of cancer so that it can be properly explained to the children. As I said, they could have easily released a real photo of Kate (instead of the shopped one) if she had been in as good condition as she appeared in the alleged video.