Did they? I thought that they mostly followed Wycliffe? Even if they didn't, one could make the argument that they used words found in the dictionary, which was not put together by believers, but that would be disingenuous.
In my extensive research of the history of the making of the KJV, I have found no evidence that the KJV translators followed the 1300's Wycliffe's Bible made from the Latin Vulgate.
It is Tyndale's that some claim is the source of 70% of the KJV's NT. The KJV translators did not have any Hebrew-English lexicons or Greek-English lexicons to use in their translation decisions since none had yet been made. They only had Hebrew-Latin lexicons and Greek-Latin lexicons, and those lexicons often gave renderings from the Latin Vulgate as their definition of Hebrew words or their definition of Greek words. There were only brief or short beginnings of anything like an English dictionary since the first comprehensive English dictionary was not printed until 1755.
According to the rules given the Church of England makers of the KJV, the KJV was officially a revision of the Bishops' Bible. The 1560 Geneva Bible was also one of their main English sources. Because the Bishops' Bible and the Geneva Bible were revisions of the Great Bible and the Great Bible a revision of Tyndale's, Tyndale's may be the indirect source with either the Bishops' or Geneva Bibles being the direct source.
The evidence is clear and compelling that the KJV translators also made some use of the 1582 Roman Catholic Rheims New Testament made from the Latin Vulgate. There is even first-hand evidence in the notes of one of the KJV translators where that translator directly asserts that the Rheims was the direct source of a rendering used in the KJV.
W. F. Moulton stated: "The Rhemish Testament was not even named in the instructions furnished to the translators, but it has left its mark on every page of their work" (
History of the English Bible, p. 207). Diarmaid MacCulloch and Elizabeth Solopova asserted that in the KJV “it was possible to see some of the readings of the Doua-Rheims version amid all the work of Tyndale, Coverdale and the Geneva translators” (Moore,
Manifold Greatness, p. 38). Ward Allen maintained that "the Rheims New Testament furnished to the Synoptic Gospels and Epistles in the A. V. as many revised readings as any other version" (
Translating the N. T. Epistles, p. xxv). Allen and Jacobs claimed that the KJV translators "in revising the text of the synoptic Gospels in the Bishops' Bible, owe about one-fourth of their revisions, each, to the Genevan and Rheims New Testaments" (
Coming of the King James Gospels, p. 29). About 1 Peter 1:20, Ward Allen noted: “The A. V. shows most markedly here the influence of the Rheims Bible, from which it adopts the verb in composition, the reference of the adverbial modifier to the predicate, the verb
manifest, and the prepositional phrase
for you” (
Translating for King James, p. 18). Concerning 1 Peter 4:9, Allen suggested that “this translation in the A. V. joins the first part of the sentence from the Rheims Bible to the final phrase of the Protestant translations” (p. 30). Allen also observed: "At Col. 2:18, he [KJV translator John Bois] explains that the [KJV] translators were relying upon the example of the Rheims Bible" (pp. 10, 62-63). The note of John Bois cited a rendering from the 1582 Rheims [“willing in humility”] and then cited the margin of the Rheims [“willfull, or selfwilled in voluntary religion”] (p. 63). Was the KJV’s rendering “voluntary” borrowed from the margin of the 1582 Rheims? The first-hand testimony of a KJV translator clearly acknowledged or confirmed the fact that the KJV was directly influenced by the 1582 Rheims. KJV defender Laurence Vance admitted that the 1582 “Rheims supplies the first half of the reading” in the KJV at Galatians 3:1 and that the “Rheims supplies the last half of the reading” at Galatians 3:16 (
Making of the KJV NT, p. 263).