Why did the police recently question Mr. Tanimoto?

The police questioned Tanimoto because they had reports that he was an American sympathizer..... that he could not be trusted.

Mr. Tanimoto had studied theology at Emory College, in Atlanta, Georgia; he had graduated in 1940; he spoke excellent English; he dressed in American clothes; he had corresponded with many American friends right up to die time the war began; and among a people obsessed with a fear of being spied upon—perhaps almost obsessed himself—he found himself growing increasingly uneasy. The police had questioned him several times, and just a few days before, he had heard that an influential acquaintance, a Mr. Tanaka, a retired officer of the Toyo Kisen Kaisha steamship line, an anti-Christian, a man famous in Hiroshima for his showy philanthropies and notorious for his personal tyrannies, had been telling people that Tanimoto should not be trusted.