In the opening verses of his gospel account, the evangelist, Mark, quotes twice from the Hebrew scriptures. He quotes, first, from the lesser prophet (Malachi being a 'lesser' than Isaiah, in certain terms) and, first, from the later prophecy (the book of Malachi coming some three hundred years after Isaiah's publication, which had significant precedence).
Thus, Mark draws attention to Malachi by quoting out of sequence to what might have been expected in terms of precedence and significance.
Mark changes one letter of what might have been (it cannot be said categorically) a quotation from the Septuagint, and in so doing he follows Jesus wording in regard to the same prophecy.
Jesus says 'my messenger' (μου) before 'thy face' (σου), who shall prepare 'thy way' (σου) before 'thee' (σου), Matthew 11:10. TR, undisputed.
Thus Jesus (followed by Mark) adds to the revelation of Malachi who states, in Hebrew, 'my messenger' before 'my face'.
Thus God says to the prophet 'my' way before 'my' face and Jesus re-states, with further definition and revelation 'thy' way before 'thy' face.
The Messenger of the Covenant, of whom Malachi prophesies, is the Lord himself. And the Lord himself is sent by Him who says 'I will prepare thy way before thy face' (as re-stated by Jesus of Nazareth and then re-stated by Mark in the introduction to his gospel account).
It becomes clear in the opening verses of Mark that a singular Messenger is being sent who will prepare the way before the Lord himself in an unprecedented manner.
And who may abide the day of his coming ? Malachi 3:2. And who shall stand when he appeareth ? He is like a refiner's fire and like fuller's soap.
There is a burning, and John was, indeed, a burning and a shining light, John 5:35.
There is a purging and a cleansing :
Whose fan is in his hand, and he will throughly purge his floor, and gather his wheat into the garner; but he will burn up the chaff with unquenchable fire. [Matthew 3:12 KJV]
The Messiah, when he comes, preceded by a previous messenger, will come with unprecedented force and with unparalleled consequence.
This is the beginning of the gospel.
John comes and faces the hypocrisy and the lethargy. His word sinks deep, and fills to the brim, as the six waterpots were filled at Cana of Galilee, before wine was available at the marriage. As the camels of Abraham's servant drank deeply, before a bride could go forth to Isaac, Genesis 25.
There is a preparatory work as the parable which is above all parables, without understanding of which one will have no knowledge of any parable, plainly declares, Mark 4:13.
The parables of the four states of ground, three of which failed due to lack of preparation, is present in the three synoptic gospel accounts but not in John. For John narrates, in detail, the ministry of John the Baptist, as such. Thus the preparative work of the Baptist's ministry is seen in reality, in John.
John stood, and Jesus appeared. Then Jesus walks by and John yet stands.
In order to follow Jesus, the disciples - first - must heed the ministry (a preparative ministry) of John. Then, he having fulfilled that ministry, Jesus appears.
But to make further progress, the disciples must leave John and follow the disappearing back of Jesus of Nazareth, the Messenger of the Covenant, the Apostle and Hugh Priest of our calling.
John came preaching and said, Repent for the kingdom of heaven is near, Matthew 3:2.
Jesus follows and repeats exactly the same words, Matthew 4:17.
The message is precisely the same, to begin with. There is absolute agreement.
But to make progress in spiritual matters, to follow Jesus unto a real salvation and an inheritance in the world to come and unto an everlasting glory - one must leave the preparatory message of John and, in faith and trust, one must follow the progress of Jesus, all the way to Jerusalem, into persecution and affliction, all the way to Gethsemane, all the way to Golgotha, all the way to the tomb and out again to the Mount and upwards to heaven . . . . . .
For John's ministry of repentance is just the beginning of the Gospel of Jesus Christ, the Son of God.
The question is astute. Which comes first ? Are they intertwined ?
This is a matter of one's own experience, I would say. Some are brought up with a little knowledge of the gospel, but perhaps unclearly. For such, they may have to be brought to a necessary understanding of the baptism of repentance, the necessity of being filled with word of a certain kind in order to, later, be able to assimilate the real and extensive word of Christ.
Some have no knowledge of religion at all. They may well begin with John and have a clear path onwards to then be enlightened further as to the gospel in full.
Yes, they sometimes seem to be 'intertwined'.
But they are distinct : preparation and fulfillment. Digging up and planting. Repentance and faith.
Only with time, maturity and experience may an individual look back and see how the Lord has led themselves. In two distinct yet absolutely necessary ways, at times, perhaps, merging but both, in their place, resulting in a deep foundation, never to be moved.
Amen.