A sudden massive drop in the overall value of CS2 cosmetic market happened around May 8. In a bit more than 24 hours, the market lost 10% of its value. Currently, the estimated market capitalization is $4.5 billion, according to Pricempire.
There's no indication of the reasons behind the sudden price drop. The losses are not the same across the entire market. Some items went up in price during the same period, while some lost half of their price.
The trading community can only speculate about what caused the price decline. Some believe that it happened naturally after the $5-billion peak, which was achieved just recently. Those who bought skins as investments could've thought it was a good time to sell, and caused a chain reaction.
There are also rumors about market manipulations in China, but one should take them with a grain of salt, as there is no concrete evidence supporting this theory. According to a series of posts by X account csgoshen dated May 3, there was a rush to buy skins preceding the price drop, possibly created intentionally in China to drive the price up.