Nebius Group N.V. (NASDAQ:NBIS) stock fell on Monday due to intense competitive threats from Meta Platforms Inc. and high-volume insider selling.The decline follows a broader risk-off trend impacting high-growth AI stocks. The Nasdaq is down 1.29% while the S&P 500 has shed 0.24%, and Technology is the weakest sector on the day.Meta Enters AI Cloud Computing MarketThe stock faced continuous downward pressure following reports that Meta is exploring an expansion into artificial intelligence computing services.The potential expansion raised investor concerns that the technology giant could become a powerful new competitor in the fast-growing neocloud market, directly impacting Nebius.Broader AI Market Pressures MountLast week, AI cloud service providers came under pressure after Samsung Electronics Co’s preliminary second-quarter results. Additionally, reports that DeepSeek is developing its own AI inference chips raised further concerns about the longevity of the broader compute buildout, accelerating the market-wide retreat from AI-related equities.Top Executives Disclose Multi-Million-Dollar Insider SalesRegulatory filings showed significant insider selling by senior Nebius executives, adding to negative investor sentiment on Monday.CEO Arkadiy Volozh sold 46,627 shares at $235.45 apiece for approximately $10.98 million. Chief Technology Officer Danila Shtan sold 16,940 shares at the same price, totaling about $3.99 million, while Chief Infrastructure Officer Andrey Korolenko offloaded 33,870 shares for roughly $7.97 million.Short Interest and Market Metrics RiseCritical Levels To Watch For NBIS StockFrom a trend perspective, NBIS is still in a longer-term uptrend, trading 24.7% above its 100-day SMA ($171.47) and 56.8% above its 200-day SMA ($136.36). But the near-term picture has weakened, with the stock 12.7% below its 20-day SMA ($244.90) and 4.1% below its 50-day SMA ($222.96), a setup that often keeps rallies "sold into" until price can reclaim those averages. RSI is 45.54, which points to neutral momentum that’s cooling rather than oversold.