I'm not sure I'm following. We have had multiple line endings (based on combinations of two particular characters) in common use, without consolidating to a common standard, for decades -- why would introducing a third character have made that more likely?

Because the reason consolidation has not happened is simple: There's no right answer, as there's no code explicitly defined by ASCII for ending a line. A major oversight.

If a code had been timely assigned, we'd have the correct way (predominant), and the legacy ways (mostly gone by now).