His predictions were being justified.
Compare the similar predictions against Edom, Isa.
He did not wait long, after his admission into that assembly, in bringing their predictions to the test.
These officials, at the command of the senate, consulted the Sibylline books in order to discover, not exact predictions of definite future events, but the religious observances necessary to avert extraordinary calamities (pestilence, earthquake) and to expiate prodigies in cases where the national deities were unable, or unwilling, to help. Only the interpretation of the oracle which was considered suitable to the emergency was made known to the public, not the oracle itself.
They give descriptions of heaven and hell, and predictions of the Antichrist.