In what ways did the discovery of the Dead Sea Scrolls help discredit the claims of those who believed that the original Bible had been lost to time and tampering?

Each manuscript nearly 100% of the time was word for word identical. The Bible was found without evidence of tampering.

It contained portions of Isaiah that was exact to the portions of Isaiah they previously had

The Dead Sea Scrolls was the ancient world speaking for ITSELF. It was proof for others that what had been taught in Churches for centuries, was the Word of God. People often say, “Seeing is Believing.” Well, there was the text. Almost word for word, what Jews and Christians had taught for years. God had preserved His Word, and in His perfect time, He would allow shepherd boys to discover the truth.