The "reason for the riddle" is that the author of the Apocalypse is a Kohen, and understands the passages which are written concerning the Kohanim, and thus, one of few who even has the right to speak or write such things.
Luke 3:2 W/H
2 επι αρχιερεως αννα και καιαφα εγενετο ρημα θεου επι ιωαννην τον ζαχαριου υιον εν τη ερημω
Luke 3:2 ASV
2 in the high-priesthood of Annas and Caiaphas, the word of God came unto John the son of Zacharias in the wilderness.
αννα και καιαφα ― Luke 3:2 ― Gematria 666
Two horns like a lamb and speaks like a dragon, (Revelation 13:11)
.
Ezekiel 28:14-16
14 You are the anointed Cherub [כרוב ממשח - Gematria 616] that covers; and I have set you so: you were upon the holy mountain of Elohim; you have walked up and down in the midst of the stones of fire [the Ephod breastplate and the two shoulder stones - LXX contains all fourteen stones of fire and the gold].
15 You were perfect in your ways from the day that you were created, until iniquity was found in you.
16 By the multitude of your merchandise they have filled the midst of you with violence, and you have sinned: therefore I will cast you as profane out of the mountain of Elohim: and I will destroy you, O covering Cherub, [כרוב הסכך - Gematria 333] from the midst of the stones of fire.
John 19:15 W/H
15 εκραυγασαν ουν εκεινοι αρον αρον σταυρωσον αυτον λεγει αυτοις ο πιλατος τον βασιλεα υμων σταυρωσω απεκριθησαν οι αρχιερεις ουκ εχομεν βασιλεα ει μη καισαρα
John 19:15 ASV
15 They therefore cried out, Away with him, away with him, crucify him! Pilate saith unto them, Shall I crucify your King? The chief priests answered, We have no king but Caesar.
The only currency allowable for use in the Herod Temple was the Tyrian Shekel:
Shekel of Tyre ―
Tryian Shekel (Melqart Baal) ― Prince & King of Tyre (Ezekiel 28).
But the chief Kohanim joined themselves unto Caesar when they cried:
"We have no king but Caesar", (John 19:15).
כרוב הסכך (kərūḇ has-sōḵêḵ) ― Ezekiel 28:16 ― Gematria 333
καισαρα (Caesar) ― John 19:15 ― Gematria 333
כרוב הסכך (Cherub of the covering) + καισαρα (Caesar) = Gematria 666
But of course if you, like most literalist futurists, insist that the authorship of the Apocalypse must be dated late first century, (generally circa 95-96AD is the time frame proposed), then your paradigm master will not allow you to see these things because they do not comply with your self-imposed prerequisites.