Probably similar to the initial confusion after 9/11, when it was speculated tens of thousands might have succumbed. Then they started going through employee rosters, and discovered the total number was about 3,000. It always seemed a little strange - and way high - that the initial worst-case estimate for the fires was 1,000 dead. These aren’t skyscrapers. People have cars, can drive around.
People in cars were blocked from leaving by concrete blocks. They couldn’t drive out. The ones that left went offroad, whether on root or otherwise. I have no idea why they put up concrete blocks so quickly, unless the authorities wanted them dead.
Anyone can get on TV or the internet and claim that they have dozens of missing friends and relatives. And then someone else tells about THEIR dozens of missing friends and relatives … and a lot of them are either non-existent or (in the case of legitimately missing people) there are multiple people reporting the same missing ones.
Once they get to the point where they have to provide actual names and details about those “missing” people, reality has a way of taking over the narrative.
They blocked people from leaving. What part of that don’t you understand?