Didn't John the Baptist preach the gospel of the kingdom, and he was baptizing the people?

Matthew 3:1 In those days came John the Baptist, preaching in the wilderness of Judaea,

  2 And saying, Repent ye: for the kingdom of heaven is at hand.

  5 Then went out to him Jerusalem, and all Judaea, and all the region round about Jordan,

  6 And were baptized of him in Jordan, confessing their sins.

Isn't that the same that Jesus began preaching, and he was healing the people?

Matthew 4:17 From that time Jesus began to preach, and to say, Repent: for the kingdom of heaven is at hand.

  23 And Jesus went about all Galilee, teaching in their synagogues, and preaching the gospel of the kingdom, and healing all manner of sickness and all manner of disease among the people.

The kingdom of heaven was at hand, the King was there in Israel.

And Jesus continued to preach like that, preaching the gospel of the kingdom:

Matthew 9:35 And Jesus went about all the cities and villages, teaching in their synagogues, and preaching the gospel of the kingdom, and healing every sickness and every disease among the people.

Then Jesus had the twelve go out and preach the gospel of the kingdom, and healing as they went:

Matthew 10:5 These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into any city of the Samaritans enter ye not:

  6 But go rather to the lost sheep of the house of Israel.

  7 And as ye go, preach, saying, The kingdom of heaven is at hand.

  8 Heal the sick, cleanse the lepers, raise the dead, cast out devils: freely ye have received, freely give.

I have mostly heard, or read, people saying that the gospel that the twelve preached, was the same gospel that Paul preached:

I Corinthians 15:1 Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;

  2 By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain.

  3 For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;

  4 And that he was buried, and that he rose again the third day according to the scriptures:

However, until after it happened, the apostles did not understand about the crucifixion and resurrection:

Mark 9:9 And as they came down from the mountain, he charged them that they should tell no man what things they had seen, till the Son of man were risen from the dead.

  10 And they kept that saying with themselves, questioning one with another what the rising from the dead should mean.

  31 For he taught his disciples, and said unto them, The Son of man is delivered into the hands of men, and they shall kill him; and after that he is killed, he shall rise the third day.

  32 But they understood not that saying, and were afraid to ask him.

And it was even hid from them:

Luke 18:31 Then he took unto him the twelve, and said unto them, Behold, we go up to Jerusalem, and all things that are written by the prophets concerning the Son of man shall be accomplished.

  32 For he shall be delivered unto the Gentiles, and shall be mocked, and spitefully entreated, and spitted on:

  33 And they shall scourge him, and put him to death: and the third day he shall rise again.

  34 And they understood none of these things: and this saying was hid from them, neither knew they the things which were spoken.

And they initially discounted the women who told them that Jesus had risen, until Jesus appeared to them.

Apparently, then, the twelve were not preaching the death, burial, and resurrection of Jesus, when they were earlier preaching the gospel of the kingdom.

Preaching the gospel of the kingdom, that the kingdom of God was at hand, because the King had come to Israel, is different than what Paul preached, later:

Acts 20:24 But none of these things move me, neither count I my life dear unto myself, so that I might finish my course with joy, and the ministry, which I have received of the Lord Jesus, to testify the gospel of the grace of God.

Paul preached the death, burial, and resurrection of Jesus, and that we're saved by grace through faith, believing the gospel:

Ephesians 2:8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:

  9 Not of works, lest any man should boast.

Paul was not preaching that the kingdom of God was at hand, because that was the message to Israel, which they rejected.

But Paul preached, to the Jew first, and also to the Greek:

Romans 1:16 For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek.

It was a different dispensation:

I Corinthians 9:17 For if I do this thing willingly, I have a reward: but if against my will, a dispensation of the gospel is committed unto me.

It is important not to confuse the dispensational difference between the gospel of the kingdom, before the cross, and the gospel of grace in the church age.

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