Somebody had a very large amount of Solena. They took out some sort of loan (getting other cryptocurrencies) using their Solena as collateral. This would have been for less than the face value of the Solena. It was quite obvious that they then planned to default on this loan and they were using it to exit their position. This would mean that whoever lent the other cryptocurrencies would take control of that Solena and try and sell it. There was very low liquidity, soo much that if they tried to sell it, it would crash the price (which is based on recent-ish sales and isn't really accurate as a result) - hardly anybody was buying Solena, so the price as is didn't reflect what would happen if a large amount went up for sale.

Solend realised this, and took a vote on seizing this amount (effectively removing the tokens from the owner's ownership and preventing them from exiting their position) requiring only 1% of token holders to approve. The vote passed. Now they've backtracked.