As Mr. Zarrab sits in jail in the United States, having been denied bail, his case has again captured the imagination of many Turks who believe the original corruption inquiry was swept under the rug and who now hope that an American court will achieve what Turkish courts were unable to: a full and fair hearing of corruption allegations that touched the highest levels of government here.

The 2013 inquiry mainly focused on corruption in the construction business and the public financing of real estate development. It also cast a spotlight on an issue that had long been a concern of the United States: the role of Turkey in helping Iran evade international sanctions over its nuclear program. One of the targets was the chief executive of the state-owned Halkbank, which the United States had long accused of working with Iran to evade sanctions in a scheme that involved using gold to buy Iranian oil and gas.

Mr. Zarrab was accused of aiding that scheme, but he was exonerated in Turkey after his arrest in 2013. The United States indictment, though, does not mention Halkbank. It lists numerous counts of money laundering and bank fraud, and it accuses Mr. Zarrab and others of conspiring for years “to violate and evade United States sanctions against Iran and Iranian entities,” Mr. Bharara said in a statement released this week with the indictment.

Mr. Zarrab’s arrest has given many Turks something to smile about this week as they are otherwise unnerved by a series of terrorist attacks, including a suicide bombing last weekend on Istiklal Avenue, Istanbul’s long pedestrian shopping street in the heart of the city’s European quarter.

It is unclear whether the American investigation intersects at all with the allegations Mr. Zarrab faced in Turkey. But critics of the Turkish government, who say the corruption inquiry was silenced through firings of the police and prosecutors who carried it out, are hoping that Mr. Zarrab, in trying to save himself, sings, and sings loudly.

Two articles, side by side, in Thursday’s Hurriyet Daily News, a Turkish newspaper, highlighted the divergence of Turkish and American justice. One reported that an arrest warrant had been issued for a Turkish prosecutor involved in the original graft case; the other was about Mr. Zarrab’s having been denied bail in the United States.