The point of passive investing and a balanced strategy is that you can’t predict what will happen. So, yes, the past five years were good for VTSAX. But if you’re investing today, then it’s the next five years that matter, not the past five years, and nobody can predict what will happen.

(Well, to be more accurate, some fund managers will predict correctly, but you can’t predict which ones. Just like you know ~50 out of 100 coins will land heads, but you can’t predict which ones, not even if you choose the one that landed heads in the last 6 throws.)