KRE: The SPDR® S&P® Regional Banking ETF seeks to provide investment results that, before fees and expenses, correspond generally to the total return performance of the S&P® Regional Banks Select Industry Index (the "Index")
VNQ: Goal is to closely track the return of the MSCI US Investable Market Real Estate 25/50 Index.
From what I understand it's the ratio (regional banks)/(RE prices), I think regional banks make most of their money lending for real estate purchases, from morgages.
If the ratio gives some heads up to other ones you can make money ezpz.
The graphs lost correlation maybe this means some mispricing. Or warns of a big crisis. Not sure what the bank/RE ratio means, maybe what share of their profit is from RE, or how expensive/cheap they are compared to RE...