because there are more fatcors tyhan just 76%.
if you miss a ft, the following ft has a different change of going in. same could be said for the 3rd one after missing the first 2. because your model lacks those stats and other real world factors your model is flawed.
like for example it being a road game. or for example. players have for example different ft% for back to back or 1 day rest or 3 days rest! or on the road ft's have different changes of going in
your statiscal value fails because it is a simplified version of very complex, real world complex thing.
EDIT: i dont blame u. I blame the educational indoctrination system. thought u that .24^3 is SCIENCE.