Massachusetts Mutual has nearly $235B in assets, so $100M is just a pittance, but it's surely an interesting investment for the staid, 170-year-old life insurance company.The Bitcoin (BTC-USD) was purchased through NYDIG (formerly New York Digital Investment Group), a fund manager with about $2.3B of cryptocurrency under management. Alongside, Mass Mutual purchased a $5M stake in the company.NYDIG founder and Chairman Ross Stevens says MassMutual isn't the first insurer to purchase Bitcoin through his company. He notes that invisible interest rates have insurers hungry for some sort of yield with which to make good on their obligations.In price action today, Bitcoin continues to meander just above $18K. The Grayscale Bitcoin Trust ([[GBTC]] +2.9%).