Here is what the Haydock Bible has for notes
Ver. 20. Tell no one that he was Jesus, the Christ. In some manuscripts both Greek and Latin, the name Jesus is not here found, and many interpreters think it superfluous in this place. The Greek expressly says the Christ adjoining the article, which the Latin tongue does not express. (Bible de Vence) — “In a preceding part of Scripture, Jesus sending his apostles, commanded them to publish his coming; but here he seems to give a contrary mandate, tell no one, &c. but in my opinion it is one thing to preach the Christ, and another to preach Christ Jesus; for Christ is a name of dignity, but Jesus is the particular name of the Redeemer.” (St. Jerome) — He did not forbid them to teach that there was a Messias a Redeemer, but to declare then that he was the person; 2d. the disciples (Matthew x,) are not sent to preach the gospel, strictly speaking, but only to prepare the minds and hearts of the people for the coming of the Messias, as is evident from Matthew x. 23. See Mark xiv. 61. and 62. John v. 18. and viii. 58. and x. 30. and xi. 27. But why did he lay this injunction? To avoid the envy of the Scribes, and not to appear to raise his own glory. He wished the people to be induced to own him for their Messias, not from the testimony of his retainers, but from his miracles and doctrines; and lastly, because as his time was not yet come, the apostles were not yet fit to deliver, nor the people to receive, this grand tenet. (Mat. Polus.) — It might moreover have proved a hinderance to his death.
The people could not yet understand that He was the Messiah, the Suffering Servant of Isaiah. They expected a king, not a sacrifical victim. The apostles had finally begun to make this connection, but it would take until after the crucifixion, the resurrection, and the coming of the Holy Spirit before the Apostles would understand fully how Jesus in his death fulfilled this roll.
Just imagine what the world would be like if they had made him king instead of crusifiying him.
