A seasonal and interesting etymology question: was the X a "commercializing" thing to make Christmas more edible for non-Christians? Is the X really a cross?

Neither, in fact; it appears that the X is really the first letter of the word Xtos (ΧΡΙΣΤΟΣ), which in Greek is the word for Christ.

Xmas

SYLLABICATION: X·mas
PRONUNCIATION: krsms, ksms
NOUN: Christmas.
ETYMOLOGY: From X, the Greek letter chi, first letter of Greek Khrstos, Christ. See Christ.
USAGE NOTE: Xmas has been used for hundreds of years in religious writing, where the X represents a Greek chi, the first letter of , “Christ.” In this use it is parallel to other forms like Xtian, “Christian.” But people unaware of the Greek origin of this X often mistakenly interpret Xmas as an informal shortening pronounced (ksms). Many therefore frown upon the term Xmas because it seems to them a commercial convenience that omits Christ from Christmas.