Pinduoduo, an e-commerce platform, takes the path of small profits but quick turnover. Basically, the merchants have pressed the price to the lowest. Merchants can get ex-factory prices to squeeze other businesses to death, and college students can't compete with others.
Now all e-commerce platforms need to spend money on the platform if they want to get exposure. College students have no funds to compete with others and no exposure. Naturally, no one will come to buy things.
And now the ecology with many products is basically stable.