Runescape has been that game wherein most people are just grinding for the money, and it's nothing really new to meet people who are selling and buying cryptocurrencies. They will add you on Discord groups to facilitate the transaction before the trade happens, and they don't really ask for much information as long as you have the money/in-currency and that's pretty much about it. Kinda like P2P trades happening on crypto though this time you don't trade real money but rather in-game currency, and the devs of the game don't really bother much about it.