Looks like you know little or nothing about this matter. The Hebrew and Greek texts from which the KJV is translated are the traditional texts SUPPORTED BY THE MAJORITY OF MANUSCRIPTS. And that goes for Mark 16:9-20.
Kindly read and carefully study The Last Twelve Verses of Mark by Dean John William Burgon, as well as all his books and articles on the true and false texts of Scripture. Then, and only then, will you be able to understand this matter.
Nehemiah, don't be facile! The only reason that there are more Byzantine texts, is because sometime much later, the Greek monks started copying the Byzantine manuscripts. It was a full time job for thousands, for generations, for centuries. The only problem, is that everyone of these manuscripts are categorized into families. So, a family called A, with 10,000 mostly identical copied manuscripts, counts as ONE manuscript.
And within families, the art of lower criticism has catalogued every single addition in the margin, copied into the text by the next generation, which is why there are so many additions in the later, corrupted manuscripts. Here is a link for you, to see that there were no Byzantine manuscripts before the 6th century existance. They just sort of sprang into being. No history, no background. Unlike the Alexandrian, which is condemned because it came from Egypt, where knowledge was flourishing and so was the Christian Church. (The Roman numerals indicate the years. So, V = 6th Century. (Red letters are highlighted by me!)
http://bibletranslation.ws/manu.html
"Note that the Byzantine classification does not show up a lot before the 6th century.
The reason for the proliferation of Byzantine branch Greek manuscripts later, is that the Byzantine church was the only one that spoke and read Greek, and so was the only branch of the church that needed to reproduce Greek Bibles. Thus the fact that there are a greater number of Greek manuscripts in the Byzantine branch is not considered significant for purposes of finding the original reading. This is not Westcott and Hort. It is just common sense.
The
Alexandrian branch is characterized as: Conservative. Relatively free of harmonization and paraphrase. Short. Willing to accept difficult readings.
The
Byzantine branch is characterized as: Widespread. Regarded by many text critics in the 20th century to be far-removed from the original documents, but worthy of detailed study because of the influence it has had on mixed manuscripts. Marked by smooth and easy readings and by harmonizations, but rarely indulges in paraphrase or the major expansions seemingly found in the Western text. It rarely creates readings. The Byzantine branch used to be widely regarded as derived from other text-types; and usually preserving the easiest reading. However, the most current studies show that many individual Byzantine READINGS are as ancient as any other.
The
Caesarean branch is characterized as: Mildly paraphrastic, so as to give an appearance of falling between the Alexandrian and "Western" texts. Since no pure manuscripts are known, most other descriptions of the type have been conjectural. To date found only in the gospels.
The
Western branch is characterized as: Marked by paraphrase, occasional expansion, and possible additions from oral sources. Fond of striking and abrupt readings. Reaches its most extreme form in D (05, Codex Bezae); the "Western" text of Paul (found in D 06) is a much more restrained text."
Time to do a little more work, instead of swallowing this Byzantine manuscripts lie!