Valve created their official Steam marketplace way back in 2013, and initially, buying, selling, and trading skins for various games was part of the experience and many users found it fulfilling to buy and sell skins for various esports titles online, however, it didn't take long for users to start having issues with the new platform. Even today, let alone in its infancy, the Steam market had its own fair share of issues and practices that were not very user friendly.
One of those unpleasant sides of trading digital items on Steam was the seven day period that players had to wait before they could sell or trade a specific skin. This practice applies when trading specific items even today and a lot of users found this unpleasant at least and very annoying at most, after all, they either received the item as a reward or bought it. It belonged to them so why should they wait. While Valve claimed that this seven day trading wait period was due to safety reasons, many were unsatisfied. This combined with additional restrictions such as users not being able to withdraw their money from the platform and were forced to spend their cash within the marketplace caused many to look around for other skin trading websites that offer services without the drawbacks, and OPSkins was happy to oblige.
People at OPSkins somehow found a way to circumvent the seven-day trade restrictions for every digital item and offered expresstrade for all CS: GO skins, which didn't sit well with Valve at the time. Eventually, OPSkins became a famous online community market and the website grew larger and more popular with every new trade. This news broke out and they didn't sit well with Valve so, in June 2018, the company took down the OPSkins website for violating the terms of service for circumventing the trade period.
OPSkins has not been providing trading services for CS: GO or any other games ever since and likely will not do so any time in the future. The marketplace that once used to have a huge digital trading community appears to be out of order for good, however, its story remains a piece of CS: GO, esports, and video game history.