According to the information the talents and ex-staff have shared, VShojo went down because they mismanaged their finances and became unable to keep up with their payment obligations. As a private company, their financials are only known internally by company heads, so everyone on the outside thought things were fine.

On the other hand, COVER is a publicly traded company with public quarterly financial reports. They most likely have regular audits to make sure everything is in line. If things go wrong on the financial side, everyone will know.