Every walled garden startup seeks to establish a monopoly as a middleman connecting users and sellers. First they loss-lead and/or fake shit to attract users, then their capture of users obliges sellers to likewise become captured. Once this monopolistic middleman position is obtained, the only way to make a profit is to undermine the quality of the connection for both sides.
Billions of VC money drives this cycle, but hope lies in how shitty the gardens become.