Spot exchange-traded funds might have excited institutional investors of Bitcoin (CRYPTO: BTC), but the frenzy is yet to catch up on retail. What happened: The King Coin’s social activity dipped significantly since peaking on the ETF approval day in early January, according to LunarCrush. Social activity is a widely used metric in crypto circles to gauge the sentiment among retail investors, a proxy for private individuals with small holdings. The data shows that socially-driven engagements like views, likes, comments, and retweets declined in the last four months. Posts by cryptocurrency cont…