LONDON/WASHINGTON—The insurgent Taliban took over Afghanistan with astonishing speed, but it appears unlikely that it will prove equally as fast in gaining control of most of the Afghan central bank’s roughly $10 billion in assets. The country’s central bank, Da Afghanistan Bank (DAB), is thought to hold foreign currency, gold, and other treasures in its vaults, though the exact contents are unclear, according to an Afghan official. Reuters was unable to reach Afghan central bank officials. The bank’s governor, Ajmal Ahmady, said in a Twitter thread he left deputies in charge of the bank on Sunday, later flying out of Kabul airport after President Ashraf Ghani and other key officials had already fled. Ahmady did not respond to Reuters’s emails and messages seeking comment. The Taliban said in a statement on Saturday that the treasury, public facilities, and government offices were the property of the nation and “should be strictly …