All-Time Low Mortgage Rates!

Before coronavirus, the average 30yr fixed mortgage rate was almost always 1.6% to 2.0% higher than 10yr Treasury yields. When bond volatility was extreme (especially when Treasury yields were dropping quickly), that gap could be wider, but it was never even close to current levels. Why might this be?
Source: Kevin Litwicki MBSLIVE
All-Time Low Mortgage Rates!