Because their fools
Men like the opinions to which they have become accustomed from their youth; they defend them and shun contrary views; and this is one of the things that prevent men from finding the truth, for they cling to the opinions of habit."-Moses Maimonides (1135-1204), The Guide for the Perplexed
the TR primarily resulted from the work of a Dutch Roman Catholic priest and Greek scholar by the name of Desiderius Erasmus, who published his first Greek New Testament text in 1516. The first edition of Erasmus' text was hastily and haphazardly prepared over the extremely short period of only five months. (ibid., page 106) That edition was based mostly upon two inferior twelfth century Greek manuscripts, which were the only manuscripts available to Erasmus "on the spur of the moment" (ibid., page 99).
The Greek New Testament project was seen by its publisher, Johann Froben, as a considerable commercial opportunity. (ibid., pages 98 and 102-103) Accordingly Froben expeditiously negotiated with Erasmus, who had already nobly intended to produce a Greek-Latin parallel text New Testament for the primary purpose of allowing Latin readers to become better acquainted with the original New Testament text, which he wanted to approximate as best as possible. Froben rushed Erasmus' first edition text to market, in his attempt to get it into circulation ahead of the much more methodically prepared Complutensian Polyglot Bible, which was due to be published soon. (In contrast to the five months that Erasmus used to hurriedly put his text together and get it printed and circulated, the Complutensian text required eighteen years of careful preparation before its first edition appeared. Erasmus himself said in a letter in Latin in 1516 that this first edition had been "praecipitatum verius quam editum," -- more precipitated than edited.)
Erasmus' Greek manuscript basis. Erasmus' final 1535 edition still relied upon no more than six Greek manuscripts, the oldest (but least used!) of which was from the tenth century. Though Erasmus did in later editions of his work consult the Complutensian version of the Greek New Testament, Metzger is able to truthfully state:
Thus the text of Erasmus' Greek New Testament rests upon a half-dozen minuscule manuscripts. The oldest and best of these manuscripts (codex I, a minuscule of the tenth century, which agree agrees often with the earlier uncial text) he used least, because he was afraid of its supposedly erratic text! [Metzger, p. 102]]
The TR was used as the basis for the KJV and all the principal Protestant translations in the languages of Europe until 1881, when the Revised Version [RV] was first published in England. The KJV translators most directly relied upon the 1598 Greek text by the Theodore de Beze of Geneva, but it also was virtually identical with Stephanus' 1550 and 1551 Greek texts, which were virtually identical with Erasmus' 1535 Greek text. Again, these all were noble efforts, but the editors of these editions did not have access to the current wealth of ancient documents and to today's more scientific knowledge of how those documents had been transmitted and partially corrupted over many centuries.
Due to the errors in the Hebrew and Greek texts from which the KJV were translated, the KJV contains some texts that are not consistent with Jesus' genuine teachings and other genuine New Testament teachings, as represented in the earliest Greek texts of the New Testament. For example:
(1) In Matthew 19:29 and Mark 10:29, the earliest and best available Greek manuscripts conclusively show that the words "or wife" (Greek: e gunaika, Strong's: #2228 and #1135) were not in the original Greek text and are contrary to Jesus' consistent, genuine teachings about marriage.
Note: See a thorough examination of Jesus' teachings and other New Testament teachings regarding marriage and separation at http://www.bibletexts.com/terms/divorce.htm.
(2) In Matthew 5:22, "without a cause" (Greek: eike, Strong's: #1500) was not in the original Greek text of Matthew.
Note: See a textual commentary of "Mat 5:22" at http://www.bibletexts.com/verses/v-mat.htm. See also S&H 369:31-32.
(3) In some cases whole verses or large parts of verses, such as 1 John 5:7-8 (as noted above), were added at the behest of church authorities who, according to some very reputable scholars, presented to Erasmus forged manuscripts in order to include texts that justified their teachings.