From the Chronicles Saga of what Soma had read, Mark was once an orphan without any flashy background; he was just a run-of-the-mill person who, luckily, received the system to fight those monsters that threatened humanity.
One of the things traits that Mark had that could make him enter the prestigious academy was a tenacious and competitive heart; he got accepted into the academy and underwent his first-year studies before everything changed as Gary Thompson easily beat him in one of the P.E. classes.
These two were completely different when Mark came from an ordinary lineage; Gary came from a golden lineage in which his father and mother were the people who ran one of the guilds in America.