No, they needed to find support so they invented it.
Can you show me where in Isaiah the servant is called a messiah? Just a chapter and verse so I can look it up. If the servant isn't called a messiah then there is no question about why he might suffer a disease.
But extra points if you understand who is saying this. It might clear up what it means.
Then you don't understand "our". Here, the Malbim can explain it: ר"ל איש מכאובות ע"י אחרים שהכל מכים ומכאיבים אותו במכות אכזריות, וידוע חולי מעצמו יש בו חולי מתדבקת מושרשת בו מיצירתו
Isaiah 53 begins with the words of the prophet Isaiah to Israel: 'Who hath believed our report? and to whom is the arm of the LORD revealed?'
Isaiah knew that old Israel would be slow to believe the message that he had to deliver!
But in this
one chapter we have the following expressions of the vicarious suffering of the Lord's
Righteous Servant [53:11].
1. 'He bore our griefs;'
2. 'He carried our sorrows;'
3. 'He was wounded for our transgressions'
4. 'Bruised for our iniquities;'
5. 'The chastisement of our peace was upon Him;'
6. 'By His stripes we are healed;'
7. The Lord hath laid on Him the iniquity of us all;'
8. 'For the transgression of My people was He stricken;'
9. 'When Thou shalt make His soul an offering for sin;'
10. 'He shall bear (or, carry) their iniquities;'
11. 'He bare the sins of many'.
Christians know that Jesus Christ fulfilled all these prophecies as the R
ighteous Servant. Ask yourself, Does a righteous servant carry their own disease? [Exodus 15:26] If you believe the scriptures, then the answer must be 'No'.
So does Isaiah tell us that the Righteous Servant was also to be the Messiah? Sure he does!
Isaiah 55:3,4,5:
'Incline your ear, and come unto me: hear, and your soul shall live; and I will make an everlasting covenant with you,
even the sure mercies of David.
Behold, I have given him
for a witness to the people, a leader and commander to the people.
Behold, thou shalt call a nation
that thou knowest not, and nations
that knew not thee shall run unto thee because of the LORD thy God, and for the Holy One of Israel; for he hath glorified thee.'
Isaiah lived well after David, so this prophecy must be about the Son of David, the Messiah. Only the Messiah can make the covenant everlasting.
David, son of Jesse, is called a servant of God, yet he became a messiah. The Son of David, Jesus, fulfilled the role of a righteous servant whilst anointed as Messiah, yet only sat upon his throne following his resurrection and ascension to heaven.
So Isaiah says, 'nations that knew not thee [i.e.Gentiles] shall run to thee because of the LORD thy God, and for the Holy One of Israel'.
Nations run to the representative of Israel, the righteous Servant and Messiah, Jesus Christ.
The difference between the Israel of the old covenant, and the Israel of the new covenant all boils down to sin. The Israel of the new covenant is the body of Christ, made up of Jew and Gentile. It is made sinless by the vicarious sacrifice of Jesus Christ.
The picture of this is given in the Exodus and wanderings in the wilderness. Who, amongst the Israelites in the wilderness, were not permitted to enter the Promised Land? Was it those born in Egypt, or those born in the wilderness [the born-again?] Was Moses permitted to enter the Promised Land?