When Pompey subdued Jerusalem (63BC), one of his first acts was to enter into the Jew’s most sacred place. It is here that the historian Tacitus (56-117 AD) says that Pompey discovered that the Jewish mysteries were empty:

[5.9] Gnaeus Pompeius was the first of our countrymen to subdue the Jews. Availing himself of the right of conquest, he entered the temple. Thus it became commonly known that the place stood empty with no similitude of gods within, and that the shrine [mysteries] had nothing to reveal [were a sham].

The Jewish religion became, in Tacitus’ eyes and in the eye’s of his contemporaries, a laughingstock. The Jews had an empty secret inner temple. Pompey and the other Greeks were looking for a revelation in the secret inner chamber, as with the other mystery cults of the time. Their mistake was thinking that the Jews were just another mystery cult. But the Jews thought that God inhabited the temple. The temple was the conduit by which God communed with man. Aslan explains:

The entire liturgy is performed in front of the Temple’s innermost court, the Holy of Holies— a gold-plated, columnar sanctuary at the very heart of the Temple complex. The Holy of Holies is the highest point in all Jerusalem. Its doors are draped in purple and scarlet tapestries embroidered with a zodiac wheel and a panorama of the heavens. This is where the glory of God physically dwells. It is the meeting point between the earthly and heavenly realms, the center of all creation… It is a vast, empty space that serves as a conduit for the presence of God, channeling his divine spirit from the heavens, flowing it out in concentric waves across the Temple’s chambers, through the Court of Priests and the Court of Israelites, the Court of Women and the Court of Gentiles, over the Temple’s porticoed walls and down into the city of Jerusalem, across the Judean countryside to Samaria and Idumea, Peraea and Galilee, through the boundless empire of mighty Rome and on to the rest of the world, to all peoples and nations, all of them— Jew and gentile alike— nourished and sustained by the spirit of the Lord of Creation, a spirit that has one sole source and no other: the inner sanctuary, the Holy of Holies, tucked within the Temple, in the sacred city of Jerusalem.

God had physically abandoned the temple in Ezekiel 10:18:

Eze 10:18 Then the glory of the LORD departed from the threshold of the temple and stood over the cherubim.
Eze 10:19 And the cherubim lifted their wings and mounted up from the earth in my sight. When they went out, the wheels were beside them; and they stood at the door of the east gate of the LORD’s house, and the glory of the God of Israel was above them.
…
Eze 11:22 So the cherubim lifted up their wings, with the wheels beside them, and the glory of the God of Israel was high above them.
Eze 11:23 And the glory of the LORD went up from the midst of the city and stood on the mountain, which is on the east side of the city.

The Jews still used the temple as their conduit to God, but God did not dwell in the temple. Instead, the Jews were under the understanding that God would return one day (Eze 43), bringing judgement and a new rule. At that time, God would again dwell with mankind:

Rev 21:2 Then I, John, saw the holy city, New Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband.
Rev 21:3 And I heard a loud voice from heaven saying, “Behold, the tabernacle of God is with men, and He will dwell with them, and they shall be His people. God Himself will be with them and be their God.

But all of this was lost on Tacitus and Pompey, they saw the Jewish religion as silly and sub-par to the Greek mysteries.

The Greek mysteries were religious cults centered around various Greek gods. The purpose of these cults were to give their adherents an introspective and self-enlightened experience. What might Pompey have expected? Hippolytus (170–235 AD) claims that the highest innitiates of the Eleusian mysteries experienced a solitary ear of corn.

And after the Phrygians, the Athenians, while initiating people into the Eleusinian rites, likewise display to those who are being admitted to the highest grade at these mysteries, the mighty, and marvellous, and most perfect secret suitable for one initiated into the highest mystic truths: (I allude to) an ear of corn in silence reaped. But this ear of corn is also (considered) among the Athenians to constitute the perfect enormous illumination (that has descended) from the unportrayable one…

Although a Christian apologist speaking of the most secretive rites of a pagan cult are to be taken with a grain of salt, it is not unreasonable that the inner chambers of the mystery religions held such mundane focus items. The purpose of the mystery cults were largely some sort of self enlightened ascension. The focus item would possibly be simple (profound) to heighten this experience.