The Direxion Daily MU Bull 2X Shares (MUU), a leveraged ETF tracking Micron Technology, experienced a sharp after-hours plunge of 5.37% on Monday. This decline followed a significant gain in the regular trading session, highlighting heightened volatility in the memory chip sector.

The sudden drop coincided with the release of Samsung Electronics' second-quarter earnings, which showed a staggering 19-fold year-on-year surge in operating profit, driven by explosive demand for AI memory chips. Despite the stellar results, market sentiment turned negative as investors grappled with concerns about intensifying competition, potential overcapacity, and the sustainability of massive AI investments in the semiconductor sector. This triggered a "sell the news" reaction across related assets.

Broader analyst commentary questioning how long the memory chip rally can last added to the pressure. Reports have highlighted that the core logic driving the sector's gains—continuous upward revisions to earnings expectations—is losing momentum, shifting focus to the actual delivery of results. Furthermore, discussions about whether South Korea's massive factory investments signal a peak in the memory cycle have fostered caution, leading to profit-taking in after-hours trading.