Why is Zhang Jian's business in the sea "the biggest joke since the Tang Dynasty"

In ancient times, scholars paid attention to agriculture, industry and commerce. Scholars are nobles and businessmen are rich, but they are the bottom of society. Many dynasties had rules that businessmen were not allowed to be officials or even wear good cars.

As the top scholar, Zhang Jian is the best in this class. However, he gave up his identity and fame in the future and resolutely went into business and became an untouchable. This kind of thing is very incredible. So at that time, it was said that his going into business was "the biggest joke since the Tang Dynasty".