If the appearance of John the Baptist onto the scene seems like a strange vision out of the Old Testament, that's not too far from the truth. Jesus would identify John as a second "Elijah" (Matt. 11:14), whom Malachi predicted would come "before the great and terrible day of the LORD" (Mal. 4:5). So he really is the last to arrive in a long line of Old Testament prophets.
Sometimes I wonder what the deal is with John's camel hair outfit, leather belt and honey-coated locust snacks. If he weren't such a deadly serious guy, I'd be tempted to think maybe this was some shtik of his, as a way of saying, "Hey, look at me, I'm a prophet!" But when you consider that he is preaching the imminent fires of judgment, it all makes sense. John the Baptist is living as a man completely divorced from the pleasures and comforts of this world in preparation for the world to come. He thinks Judgment Day is coming at any moment: "You brood of vipers, who warned you to flee from the wrath to come?" "The axe is already laid at the root of the trees." "He will burn up the chaff with unquenchable fire."
It turns out John was right and wrong. He was right that the Christ was coming and that the people must prepare their hearts for him through repentance. But he was wrong that the Christ was coming with the fires of judgment this time around. Judgment Day wouldn't take place until his second coming.
Here's how it was once explained to me. The Old Testament prophets perceived the future coming of Christ the way you might see the peaks of a mountain range from afar. It appears to be only one mountain range, but in truth you are actually looking at two mountain ranges, one positioned much farther behind the other. At a distance you could not tell which peaks belonged to the first range and which to the second. So here. When the OT prophets envisioned the coming of Christ, sometimes they saw suffering and servanthood, sometimes glory and judgment. They thought they were looking at one event when in fact they were looking at two. Christ would come the first time to suffer and die, then later he would come a second time to reign in glory.
Like a typical OT prophet John the Baptist conflates the first and second comings of Christ and expects the world to end as soon as Jesus arrives. But it doesn't, and this causes him some confusion. So was there egg on his face? Was his ministry totally misguided?
It turns out, no. Jesus consistently commends John's ministry because he did his job. John cleared the path by preaching a baptism of repentance. He may have thought he was preparing the people to repent with fear in view of Judgment Day. But in fact he was preparing their hearts to repent with joy, on the day Christ would go to the cross and suffer judgment on their behalf.