John the Baptist is often under appreciated in his role as the herald of Israel's/Jewish eschatology or eschaton:
Mal 3:1 Behold, I will send my messenger, and he shall prepare the way before me: and the Lord, whom ye seek, shall suddenly come to his temple, even the messenger of the covenant, whom ye delight in: behold, he shall come, saith the LORD of hosts.
John was the messenger of the old covenant in proclaiming wrath on the covenant breakers according to the blessings and curses of Deuteronomy.
Mal 3:5 And I will come near to you to judgment; and I will be a swift witness against the sorcerers, and against the adulterers, and against false swearers, and against those that oppress the hireling in his wages, the widow, and the fatherless, and that turn aside the stranger from his right, and fear not me, saith the LORD of hosts.
Mal 3:7 Even from the days of your fathers ye are gone away from mine ordinances, and have not kept them. Return unto me, and I will return unto you, saith the LORD of hosts. But ye said, Wherein shall we return?
Jesus stated that John was the messenger of Malachi:
Matt 11:9 But what went ye out for to see? A prophet? yea, I say unto you, and more than a prophet.
Matt 11:10 For this is he, of whom it is written, Behold, I send my messenger before thy face, which shall prepare thy way before thee.
John warned the vipers that the axe was laid at the root, and that the swing of the axe was impending.
Matt 3:10 And now also the axe is laid unto the root of the trees: therefore every tree which bringeth not forth good fruit is hewn down, and cast into the fire.
John was not the herald/messenger of a wrath to come 1970 years later and counting.
The fact that he was threatening wrath according to the old covenant means that covenant could not "pass away" until that covenantal wrath was delivered and consummated which it was in the war of 66-70 AD