"Buy the rumor and sell the news" is an investment strategy that involves buying a financial asset before an event occurs that is expected to have a positive impact on its price. Once the event occurs and the price of the asset rises, the investor sells their holdings for a profit. This strategy is based on the idea that financial markets tend to overreact to news.

Within a few weeks, the Bitcoin halving will occur, an event programmed into the protocol's code that reduces the issuance or reward of BTC by half, from 900 BTC mined each day to just 450 BTC. In other words, the liquidity that miners on the network can provide to the various markets will be reduced. This seems like a small thing when you consider that most of the BTC that will exist have already been mined (more than 19 million). However, most of the BTC that were once mined are kept out of the foreign exchange markets, probably because individuals, companies, or institutions use that money for long-term profits.
Each halving has had an exhilarating effect on the price of bitcoin. A smaller amount of money in circulation relative to a higher demand causes the currency to acquire more value. That's why there's a high expectation about what might happen once emissions are cut in half. Similarly, the approval of bitcoin ETFs in the United States seems to have been the reason for many to buy the rumor and sell the news. When investors were still waiting for approval, bitcoin was worth close to USD 46,000. After approval, the price quickly bubbled up to USD 49,000. But immediately selling pressure slowed the climb, apparently, and some investors appear to have taken their profits just hours after "the news" happened.