Because with the presumption that the CPI might keep going down, giving an opportunity for Powell to achieve his "Soft Landing", then there's also the tendency that markets surge and people start spending money like a drunken sailor again because "everything is going to be OK". But let's wait for next month's CPI print after the market and the people's positive reaction for the current month.
Since the reduction of the Consumer Price Index is significant the reduction of consumer price also indicates low inflation, there are predictions that the Federal Reserve will reduce interest rates from June to September. Which means more money in the hands of American citizens and the potential of saving and investing. If the US Central Bank reduces interest rates for few times it might
trigger a price increase.
But a "price increase" of what? Prices of assets in the stock market and cryptocurrencies? It will, BUT it will also cause a price increase of goods and services simply because there's more money in circulation. What would the Federal Reserve do if the CPI starts printing hot again?