Initial reports of the situation assumed that the Ukrainian digital farm was using PS4s to farm cryptocurrency, a rare but not wholly uncommon sight. However, a closer inspection of photos from the farm made clear the consoles were PS4 Slims, which are much worse for farming cryptocurrency. With FC 25 Coins that in mind, some noticed that many of the PS4 Slims had discs sitting in their disc slots. However, it was difficult to tell what the discs were actually for.
Delo.ua was able to investigate the matter further, questioning an unnamed source regarding the PS4 Slims and the games they were running. The source described the farm using a "leveling bot" for FC and then "selling them." Perhaps something is lost in translation, but the message comes across as a very general description of what could have been happening, as opposed to a literal explanation for how the farm was using consoles to use FC games to earn money.
There are many ways that FC could be used to farm money, of course. The most fitting explanation would be selling FC Ultimate Team accounts. Since individual players can't be traded in Ultimate Team, there's a huge market for new accounts with valuable players already unlocked on them. Alternatively, the PS4 Slims could be farming FC 25 Ultimate Team Coin, FC 's currency. It may not be as lucrative as Bitcoin, but it can be farmed on PS4 Slims rather than $1.000 GPUs.
The intricacies of how the digital farm manages thousands of PS4 Slims, each independently running FC, are unclear. The basic idea is that PCs are used to run bots, which then control how each console farms currency or FC Ultimate Team packs. It had to have been a lot of work to manage.
It just goes to show what kind of economy Electronic Arts has created around buy FIFA 25 Coins and its other sports games. It has made earning FC currency and in-game content so frustrating to earn that there's a market comparable to cryptocurrency mining thriving on selling these digital products to players.