Cryptocurrencies, among the most volatile of financial assets, have fallen quiet even as turmoil has gripped stocks, bonds, commodities and traditional currencies.

Bitcoin has mostly traded around $6,500 in recent weeks, in contrast to last year’s manic rally and the steep plunge that followed this year. Enthusiasts hope muted swings could help cryptocurrencies, of which bitcoin is the largest, gain traction as a means of transaction.

Since...