assuming that there are going to be 64 matches, with a minimum seating capacity of 40000 in each stadium, that would need 2.56 million people to have a 100% attendance for all the matches
I know 100% attendance is unrealistic, but that is not the point I am making
Bear in mind that many world class stadiums have much higher capacities that 40000, can go up to twice that
Also consider that the 2010 FIFA world cup had an attendance of 3.1M and was still behind the aggregate attendance of the US and Germany
With a population of 1.7 million, its safe to say that 2022 Qatar World Cup if it ever came to pass would be one of the smaller ones in recent times when it comes to attendance