Interestingly, the level of C&I Loans as a proportion of GDP is pretty level over many decades (chart 2).
Currency can be explained by Scott Sumner's point, that the market is more indifferent about holding cash when rates are low.
I have discussed how the Price to Rent ratio for homes should increase as real interest rates decrease. This can happen through an increase in price or a decrease in rents. In practice, it appears to have come entirely from increases in real estate prices. Could it be because low risk long term securities are Giffen goods? As their values increase, the economy's propensity to hold them also increases, whether in terms of ownership of properties or bank ownership of securities.
PS. Here is a chart from this Economist article. At that site the chart is interactive. Note that house prices across the Anglosphere have followed similar trajectories for the last 40 years, until 2008. Since then, the US is the outlier. It is tempting to think that the US has reverted back to a normal valuation level, but I think this is a product of mental accounting biases. If US home prices recover to pre-crisis levels, they will be catching back up to these foreign markets.