According to Bobby Ong, altcoins are experiencing widespread declines as traders execute the well-known 'sell in May and go away' strategy on the last day of the month. This trend highlights a seasonal pattern where investors reduce exposure to riskier assets like altcoins before the summer, often leading to increased market volatility and lower liquidity. Traders should monitor key support levels and watch for potential rebounds in June, as historical data suggests a shift in sentiment post-May (Source: Bobby Ong on Twitter, May 31, 2025).