Correlation is not a static fact about two assets; it is a regime-dependent relationship. What is happening: Assets that diversify each other in calm periods can suddenly move together when liquidity dominates fundamentals. That is why diversification should be tested under stress logic, not only under average conditions. In practice: A portfolio that looks balanced in a spreadsheet may still compress into one trade when the common driver becomes funding stress. Watch for: The mistake is treating historical average correlation as a permanent law. Useful lens: A useful review question is which funding, incentive or cash-flow channel is actually doing the work. That is the kind of small conceptual habit that compounds into better decisions over time.