I was reading another article earlier today, and the article stated that they bought back some bitcoin after the market dump
According to the Forbes article they pulled back ~2k BTC but the amount they sent to exchanges was 7800 BTC. The rest was sold and caused the liquidations and the drop in spot price.
They did not buy back anything. There are articles like
this one circulating in the Internet that suggest they bought some coins back. IMO there was no buyback and many sources seem to support that. They stopped selling and moved the rest of the coins back to their wallet.
maybe their plan was probably to manipulate the market,
I don't think so. It's the government, it can't allow itself to be accused of manipulating the price, dumping to liquidate traders and buy back.
They're selling because this was seized money and they don't need a bitcoin position, but want to get EUR for it. The problem is they could get more by selling OTC, but someone irresponsible was charged with selling coins, so that person thought they were smart and moved BTC to a number of exchanges to spread it, so that it doesn't put too much pressure on 1 exchange, but I don't think they realized how shallow the market was and how deep this sale would take the price. Once they did their thing and saw the price drop by 20% they stopped.