Antichrist

That the Antichrist will claim to be the Jewish Messiah and will (at first) be falsely recognized so is the traditional interpretation, yes. The traditional interpretation is that John 5:41-44 refers to the Antichrist: I do not receive honor from men. But I know you, that you do not have the love of God in you. I have come in My Father’s name, and you do not receive Me; if another comes in his own name, him you will receive. How can you believe, who receive honor from one another, and do not seek the honor that comes from the only God? One interpretation is that Matthew 24:23-25 refers to the Antichrist: Then if anyone says to you, ‘Look, here is the Christ!’ or ‘There!’ do not believe it. For false christs and false prophets will rise and show great signs and wonders to deceive, if possible, even the elect. See, I have told you beforehand. Another interpretation is that it is rather Matthew 24:15-22 that refers to the Antichrist, who will rebuild the Jewish temple in Jerusalem (being thought to be the prophesied Messiah) but will then, to the horror of the Jews, take his seat in the Holy of Holies and claim to be God Himself, in a twisted parody of Christianity: Therefore when you see the ‘abomination of desolation,’ spoken of by Daniel the prophet, standing in the holy place … then let those who are in Judea flee to the mountains. Let him who is on the housetop not go down to take anything out of his house. And let him who is in the field not go back to get his clothes. But woe to those who are pregnant and to those who are nursing babies in those days! And pray that your flight may not be in winter or on the Sabbath. For then there will be great tribulation, such as has not been since the beginning of the world until this time, no, nor ever shall be. And unless those days were shortened, no flesh would be saved; but for the elect’s sake those days will be shortened. Likewise, in 2 Thessalonians 2:3-4: Let no one deceive you by any means; for that Day will not come unless the falling away comes first, and the man of sin is revealed, the son of perdition, who opposes and exalts himself above all that is called God or that is worshiped, so that he sits as God in the temple of God, showing himself that he is God. Revelation is a terribly difficult text to understand, but the traditional interpretation is that the Antichrist will be a Jew from the tribe of Dan, which is why this tribe is excluded from the 144,000 elect (Revelation 7:4-8). They are the Jews who will convert to Christianity because of the preaching of Elijah and the evident falsehood of the Antichrist (Revelation 11:3-13; 12; 14:1-5). As Paul prophesies in Romans 11:24-29: If you were cut out of the olive tree which is wild by nature, and were grafted contrary to nature into a cultivated olive tree, how much more will these, who are natural branches, be grafted into their own olive tree? For I do not desire, brethren, that you should be ignorant of this mystery, lest you should be wise in your own opinion, that blindness in part has happened to Israel until the fullness of the Gentiles has come in. And so all Israel will be saved, as it is written: “The Deliverer will come out of Zion, and He will turn away ungodliness from Jacob; for this is My covenant with them, when I take away their sins.” Concerning the gospel they are enemies for your sake, but concerning the election they are beloved for the sake of the fathers. For the gifts and the calling of God are irrevocable. Sometimes, Old Testament passages are traditionally interpreted as referring to this Antichrist from Dan, who at first is recognized as the Jewish Messiah but later turns out to be anything but, and to Elijah converting the Jews to Christianity as well, for instance: Dan shall judge his people as one of the tribes of Israel. Dan shall be a serpent by the way, a viper by the path, that bites the horse’s heels so that its rider shall fall backward. I have waited for your salvation, O Lord! (Genesis 49:16-18) He shall return and show regard for those who forsake the holy covenant. And forces shall be mustered by him, and they shall defile the sanctuary fortress; then they shall take away the daily sacrifices, and place there the abomination of desolation. Those who do wickedly against the covenant he shall corrupt with flattery; but the people who know their God shall be strong, and carry out great exploits. And those of the people who understand shall instruct many; yet for many days they shall fall by sword and flame, by captivity and plundering. Now when they fall, they shall be aided with a little help; but many shall join with them by intrigue. And some of those of understanding shall fall, to refine them, purify them, and make them white, until the time of the end; because it is still for the appointed time. Then the king shall do according to his own will: he shall exalt and magnify himself above every god, shall speak blasphemies against the God of gods, and shall prosper till the wrath has been accomplished; for what has been determined shall be done. He shall regard neither the God of his fathers nor the desire of women, nor regard any god; for he shall exalt himself above them all. But in their place he shall honor a god of fortresses; and a god which his fathers did not know he shall honor with gold and silver, with precious stones and pleasant things. (Daniel 11:30-38) Behold, I will send you Elijah the prophet before the coming of the great and dreadful day of the Lord. And he will turn the hearts of the fathers to the children, and the hearts of the children to their fathers, lest I come and strike the earth with a curse. (Malachi 4:5-6)

> Why both christian and muslim are so sure about Jewish messiah will be the antichrist?

de-legitimizing the Jewish idea of the Jewish messiah is perhaps the easiest way to provide evidence for why people believed Jesus was the Jewish messiah.

Christianity has always had internally explain and rationalize why Judaism continued to exist, and why the majority of Jews did not convert to Christianity.

the continued existence of a group of people from whom the messianic concept in question originated saying your guy didn't do the things required is, essentially, a massive point of theological anxiety.

Christianity has the following options when it comes to the claim that Jesus is the messiah:

1. acknowledge the Jewish messiah has different qualities than does the Christian messiah concept, so the Christian concept can exist and fulfill a totally different theological idea OR,

2. explain why the Jews do not believe in Jesus as the messiah -- usually because [it is argued] they are wrong about the Jewish messiah's requirements/prophecies, and further, prevent the idea from having any legitimacy in the future

They have historically taken option #2, and leaned into supersessionism. I assume this influenced Islam as well. Both religions have needed to justify why Jews did not all convert to their respective religions, maintained Jewishness, etc.