People still don’t appreciate how ephemeral success is.

The remark underscores how quickly reputations, winning streaks, and public acclaim can evaporate—especially in domains driven by uncertainty, competition, and shifting conditions (politics, markets, media, sports). It implies a cognitive bias: people overlearn from recent wins and treat success as proof of stable superiority rather than a fragile outcome partly shaped by luck and timing. Read in light of Silver’s broader emphasis on probabilistic thinking, the line cautions against triumphalism and encourages humility: today’s “signal” of competence can be overwhelmed by tomorrow’s noise, regime change, or simple reversion to the mean.