You must have misunderstood the news article. It didn't say they will buy what's left of FTX but they will buy or invest in cryptocurrencies because the prices are down as a result of the FTX implosion. These banks are business opportunists at the end of the day and will take a calculated risk if a chance presents itself.
Of didn't say that they were buying FTX, but crypto companies. There's no talk in the articles that they would invest in cryptocurrencies but cryptocurrency companies, and those are down because of the case FTX .
And why they do this? They see that they can get them almost free and they are in it for the long term. Many crypto companies also might have better fundamentals then most cryptos and actual value behind them. Even if they are now having hard times.
It seems to me that if they really plan to buy the companies that were hurt by the FTX collapse, this could be bullish news in the near future. After all, there were no public announcements during the entire market crash, and here comes Goldman Sachs right away. The only thing that is not clear yet is whether we can trust this news.