Because Tyson and Rocky had the same size, strength, speed and proven super heavyweight two handed power based on what exactly ?
Both fighters were great heavies. But just because tyson would beat sharkey a certain does not mean Marciano would put sharkey away the same way. Both have specialties but different ones . Marciano Sharkey would be a war for however long it lasts and Marciano would take sometime to put sharkey away . Tyson would put sharkey away faster . Marciano speciality was volume punching and great stamina stopping opponents with attrition and stamina Tyson specialty was to be very athletic , powerful, dynamic with speed and would stop opponents rather much quicker without taking as much damage as rocky did . Both great fighters nonetheless. But two different ones at that.