When the KJV translators did their work, they have thousands of manuscripts from the Majority Text available and the other texts they had were used to compare to the Erasmus text which was a complete compilation. The KJV translators used Erasmus not only because of its accuracy, but because it was convenient to use a text where all of the mss were in one volume so instead of sifting through thousand of mss, they could walk through Erasmus text and then compare verse by verse his text to the Erasmus text as well as other completed texts.
Where is the documented evidence that shows that the KJV translators had available thousands of Greek manuscripts and that the KJV translators actually directly examined, compared, or collated those Greek manuscripts?
Some of the TR editors examined some Greek manuscripts, likely less than 100. The KJV translators' knowledge of Greek manuscripts likely depended upon the imperfectly presented information in the 1550 Stephanus edition based on 15 Greek manuscripts plus Erasmus' text.
Robert Estienne or Stephanus (1503-1559) edited some editions of the Greek New Testament. The first two editions [1546 and 1549] of Stephanus' Greek New Testament were a compound of the earlier editions by Erasmus and the earlier Complutensian Polyglot. His third edition (1550) is considered to be closer to the fourth and fifth editions of Erasmus' text (Metzger, Text of the New Testament, p. 104). The edition of Smith’s Dictionary of the Bible edited by H. B. Hackett asserted that “numerous instances occur in which Stephens deserts his former text and all his MSS to restore an Erasmian reading” (III, p. 2132). KJV-only advocate Laurence Vance also noted: "The third edition in 1550 had the distinction of being the first Greek New Testament with a critical apparatus and was the standard text in England until the time of the Revised Version" (Brief History of the English Bible Translations, p. 12). Edward Hills observed that Stephanus "placed in the margin of his 3rd edition of the Textus Receptus variant readings taken from 15 manuscripts, which he indicated by Greek numbers" (KJV Defended, p. 117). F. H. A. Scrivener indicated that Stephanus in his preface stated that his sources were sixteen, but that includes the printed Complutensian as one of them (Introduction, II, p. 189). Tregelles confirmed that “the various readings in the margin are from the Complutensian printed edition and from fifteen MSS” (Account, p. 30). Brian Walton observed that Stephanus “reckons sixteen Greek copies, which he collated, and out of them noted 2384 various readings, which he though fit to put in the margin of his edition” (Todd, Memoirs, II, p. 132). Edwin Bissell maintained that “in the edition of 1550, indeed, the first collection of variations in manuscripts was actually published, numbering two thousand one hundred and ninety-four” (Historic Origin, p. 128). The Cambridge History of the Bible pointed out that "Erasmus's Greek text was to remain the principal source" for that standard 1550 text of Stephanus (Vol. 2, p. 449). Tregelles affirmed that in Stephanus' 1550 folio edition "Erasmus was almost exclusively followed" (Account of the Printed Text, p. 30). The Oxford Encyclopedia of the Reformation noted that "through its [Erasmus's Greek text] being incorporated into the third edition of Robert Estienne's Greek Testament (1550) it influenced strongly the Greek Testament of Theodore de Beza" (Vol. 2, p. 57). Scrivener noted that his “own collation represents Stephen’s first edition as differing from his third in 797 places, of which 372 only are real various readings, the rest relating to accents, or being mere errata” (Introduction, II, p. 190, footnote 3).
Has anyone ever checked and confirmed the accuracy of all of these collations? Scrivener suggested that “the degree of accuracy attained in this collation may be estimated from the single instance of the Complutensian, a book printed in very clear type” (Introduction, II, p. 190). Scrivener then indicated that “forty-eight, or one in twelve [of Stephen’s citations of the Complutensian] are false” (p. 190, footnote 1). Tregelles maintained that “it may be said, that as the Complutensian text is often incorrectly cited in Stephen’s margin, we may conclude that the same thing is true of the MSS which were collated; for it would be remarkable if manuscripts were examined with greater accuracy than a printed book” (Account, p. 31). Smith’s Dictionary maintained that “while only 598 variants of the Complutensian are given, Mill calculates that 700 are omitted” (III, p. 2131). In a note, John Eadie commented: “The margin of the New Testament of Robert Stephens, 1550, is not of great value. He did not print all the various readings which his son Henry had gathered, nor did he fully collate all the sixteen MSS” (English Bible, II, p. 214). Samuel Newth maintained that the manuscripts used by Stephanus were “imperfectly collated” (Lectures, p. 86). Frederic Gardiner claimed that the collation in this edition “is neither complete nor accurate” (Principles, p. 5). Richard Porson (1759-1808) asserted that “Stephen’s margin is full of mistakes in the readings and numbers of the MSS” (Gentlemen’s Magazine, May, 1789, p. 386; Letters, p. 55). Porson maintained that Stephens “has favored us with only a part of the various readings, (probably less than half) and has frequently set down a reading as from one manuscript which belonged to another” (Letters, pp. 88-89). Charles Hudson reported that the “various readings collated by his son” . . . “are known to be given very inaccurately” (Greek and English Concordance, p. xiv).
Donald Brake wrote: “Beza’s text was essentially that of Stephanus. Any departures generally were not on textual authority but the arbitrary choice due to his theological persuasion” (Visual History of the English Bible, p. 233). Charles Butler claimed: “In his choice of readings, he [Beza] is accused of being influenced by his Calvinistic prejudices” ((Horae Biblicae, p. 108). Edwin Bissell asserted that “Beza employed the materials in his hands principally for exegetical purposes” (Historic Origin, p. 128). Tregelles maintained that Beza "valued readings more in proportion to their theological importance in his eyes than to the testimony by which they are upheld" (Account of Printed Text, p. 33). Likewise, Scrivener asserted that Beza “exhibits a tendency, not the less blameworthy because his extreme theological views would tempt him thereto, towards choosing that reading out of several which might best suit his preconceived opinions” (Introduction, II, p. 193).