Everyone is guessing who the market maker that sold 70 million $GPS is, but it's not easy to guess.
On the day of the GPS listing, the project party transferred 800 million GPS to Binance. According to GoPlus's own statement, 500 million of those coins have clear allocations: 300 million are rewards for HODLers; 200 million are planned for future marketing initiatives (this portion has already been transferred from the Binance wallet to a separate wallet for storage).
So the dumped tokens should be the other 300 million tokens allocated to market makers. GoPlus does not allocate coins to market makers on-chain, but instead transfers the coins to Binance and then gives them to the market makers. Without on-chain allocation, it is impossible to trace which market maker it is through wallet transaction records.