I'm planning to start a strategy on SP500 hedging losses on USDJPY, because USD usually goes the opposite of SP500. I'm also considering other symbols (USDCAD, USDCHF, USDX) I just took the charts of SP500 and USDJPY and they are effectively quite uncorrelated, exception for 2008 crisis on SP500...I noticed that during 2008 also USDJPY went down...so I'm asking what are the fundamental reasons...
1 - why both SP500 and USDJPY went down during 2008 if they are uncorrelated and US dollar went up during 2008? I know that it means JPY performed better than USD if USDJPY went down, but what are the fundamental reasons?
2 - the fundamental reasons underlying the fact that both went down in 2008 can happen again so that counting on USDJPY to hedge the SP500 doesn't worth it? Because I noticed that correlation between them in the last years has been increased, in fact in 2022 there has been a high uncorrelation.