If a person becomes contaminated but does not show symptoms of the covid-19, can the symptoms appear later on? why is it some get sick, even die but most others are not affected?

COVID-19 severity: This is the same for most infections. Strep throat, pneumonia, influenza, chlamydia, and most others have a spectrum of severity from no symptoms at all through mild, moderate, and severe. Some are always severe (rabies always kills and ebola often does), but these are minority. The biological reasons for these differences are complex and not well understood; and not yet known at all for COVID-19.

No.: Symptoms does not appear 14 days after infection if did not appear during this 14 days , at least this is what is known so far. People not affected are the ones who are the winner of the war between corona virus 19 and the immune system of the persons at the begining of the lower respiratory tract which are bronchi. These are usually young people also people do not have any medical illnesses.