The virus destroyes cells in the lungs and paves the way for fungi and bacteria. These are the killers, not the virus itself. The mortality rate depends on how successful antibiotics work. Antibiotic resistance is not the same around the world: https://resistancemap.cddep.org/DRI.php Then there is a difference how many cases without symptoms got counted. And there seem to be at least five different strains of CV, not every country has all of them.