Y'shayahu / Isaiah 42 is about G-d speaking of his blind and deaf servant -- the Jewish nation. There is no mention of salvation -- that is an addition by the list maker. The light to the nations is the Jewish people -- a nation of priests designated by G-d to bring knowledge of Him to them. . .
What of the light being salvation?
In the T'nach (Jewish bible) the term salvation always refers to the rescue of the physical lives of people - it has no reference at all to the "salvation of the eternal soul" as most Christians would perceive it.
I refer you to any or all of the following examples:
• “Just stand still and you’ll see HaShem’s salvation that He is going to do for your today....” (Sh'mot / Exodus 14:13)
• “HaShem saved Israel from Egypt’s power that day....” (Sh'mot / Exodus 14:30)
• “HaShem set up a savior for Israel—Otniyél ben K'naz, Kalév’s younger brother....” (Shoftim / Judges 3:9)
• “HaShem set up a savior for them—Éhud ben Géra the Bin-y'mini, who had a deformed right hand....” (Shoftim / Judges 3:15)
• “....and he, too, saved Israel....” (Shoftim / Judges 3:31)
• “If You will save Israel through my hand, as You have spoken....” (Shoftim / Judges 6:36)
• “....you didn’t save me from them....and, when I saw that you hadn’t saved me....” (Shoftim / Judges 12:2-3)
• “HaShem saved Israel that day....” (Shmuel 1 / 1 Samuel 14:23)
• “....so David saved the inhabitants of K'ilah....” (Shmuel 1 / 1 Samuel 23:5)
• “HaShem is my Light and my Salvation--
Whom should I fear?
HaShem is the fortress of my Life--
Whom should I dread?
If evil men approach me
To devour my flesh--
[When] my adversaries and my enemies [attacked] me--
Wow! They stumbled and fell!
If an army encamps against me
My heart will not be afraid;
If war breaks out against me--
On this [assurance] I can rely!” (T'hillim / Psalm 27:1-3)
The above verses (and these are only a selection—there are many, many more) demonstrate how the verb save and nouns savior, salvation are used in the T'nach, which is nothing like the way christians use them....The list maker continues to reference Y'shayahu / Isaiah 42 as being prophetic about Jesus. Yet the chapter is clear that the Jewish people are G-d's servant in this chapter -- a servant who is described as often being blind and deaf to G-d's message (certainly not a description most Christians would ascribe to Jesus!).
Y'shayahu / Isaiah 42:5 - 6 "So said G-d the L-rd, the Creator of the heavens and the One Who stretched them out, Who spread out the earth and what springs forth from it, Who gave a soul to the people upon it and a spirit to those who walk thereon. I am the L-rd; I called you with righteousness and I will strengthen your hand; and I formed you, and I made you a covenant for the people, for a light to nations."
The concept of the servant as a light to the nations is repeated "And He said, "It is too light for you to be My servant, to establish the tribes of Jacob and to bring back the besieged of Israel, but I will make you a light of nations, so that My salvation shall be until the end of the earth."" Y'shayahu / Isaiah 49:6.
Jesus was not the servant who established the tribes of Jacob or returned the besieged of Israel -- or the light to the nations. This might fit Isaiah himself, or the real messiah or even the Jewish nation -- but it does not fit Jesus.
There is another reference to examine. "And nations shall go by your light and kings by the brilliance of your shine." Y'shayahu / Isaiah 6:3.
Isaiah 60 is definitely speaking of the Jewish people. Isaiah tells Jerusalem to rise, for their light has come. Darkness will cover the Earth, but they alone will have light. The other nations will follow their light to G-d. The Jews have been told many times that they are a nation of priests, a light to the other nations. "And you shall be to Me a kingdom of princes and a holy nation.' These are the words that you shall speak to the children of Israel."" Sh'mot / Exodus 19:6 and "Hearken to Me, My people, and My nation, bend your ears to Me, when Torah shall emanate from Me, and My judgment [shall be] for the light of the peoples, I will give [them] rest." Y'shayahu / Isaiah 51:4.
The one G-d called is the servant who is so often blind and deaf, but is still His servant -- the Jewish nation or possibly the prophet Isaiah himself -- but it does not apply to Jesus. Unsure?
Y'shayahu / Isaiah 42:19 - 20. says "Who is blind but My servant, and deaf as My messenger whom I will send? He who was blind is as the one who received his payment, and he who was blind is as the servant of the L-rd. There is much to see but you do not observe, to open the ears but no one listens."
Was Jesus deaf to G-d?
Was Jesus blind to G-d?
Answering "no" to those two questions means you reject Jesus as the subject of this chapter.
And what of being a light to the nations (goyim / gentiles)? Time and again Jesus states that he did not come for the gentiles, but for the Jews. Read Matthew 10:5-6 "“Go nowhere among the Gentiles and enter no town of the Samaritans, but go rather to the lost sheep of the house of Israel." and Matthew 15:24 "“I was sent only to the lost sheep of Israel.”
In his ministry Jesus did not reach out to the gentiles. He did help a few here or there -- but he did not have a ministry to the gentile world and never left Israel (Judah and Galilee) to preach in the gentile world.
There is nothing in Y'shayahu / Isaiah 42:5 - 6 that Jesus fulfilled.