How did the discovery of the lost Hittite civilization provide evidence in support of the biblical record?

"The Old Testament mentions the ancient Hittite civilization more than 50 times, either by their Hebrew name "Chitti" or by their designation as the sons and daughters Heth. However, prior to their rediscovery in the 19th century, there appeared to be no evidence for their existence outside of the Bible. Skeptics cited the missing evidence as evidence that the Bible actually fabricated their existence. This called the reliability of the biblical account into question. Basically the skeptics said, "We can't find any evidence for the Hittite civilization outside of the Bible. This demonstrates that the Bible cannot be trusted as an historical source."

Then, in the 19th and 20th centuries archaeologists hit the jackpot, not only identifying extrabiblical references to the Hittite civilization, but by actually finding and excavating the ancient Hittite capital city of Hattusa (modern day Boðazköy in northern Turkey). The rediscovery of this ancient civilization vindicated the Biblical record.

Evidence for the Hittites was bolstered in Egypt with the discovery of a treaty between Pharaoh Ramses II and the Hittite Empire. Originally written on silver tablets in Heliopolis and Hattusus, a huge copy was found on a wall of the great Karnak Temple. After years of fighting between the Hittites and the Egyptians, Ramses II and the Hittite king settled on a treaty whereby the territory of Syria and Canaan would be divided between them."

http://www.allaboutarchaeology.org/hittite-faq.htm