Diversification
Diversification is spreading money across assets that do not all move together, so one failure hurts less.
Holding ten coins is only diversified if they do not all fall at once. Because most large coins follow Bitcoin closely, a crypto-only portfolio is often less diversified than its number of holdings suggests; assets outside crypto, or stablecoins held as cash, diversify more.
Diversification reduces the effect of any single coin failing, but it does not remove market risk and it does not raise returns by itself. Check how closely your holdings move together with the correlation matrix.