The issue is that #CRLF# is being expanded into a new line before it's being written. Luckily, there is a fix for that. We simply need to escape the variable using * (#*Variable*#).
SKIN:Bang('!WriteKeyValue','Variables',sHolidayPrefix..'Name1','New Year#*CRLF*#Happy New Year','#RootConfigPath#\DynamicVariable.inc')
Also, note that I converted your bang to the new format used in Rainmeter 2.3.3
SKIN:Bang(Parm1,Parm2,Parm3...)
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This is the song that never ends. It just goes on and on my friends. Some people started singing it not knowing what it was, and they'll continue singing it forever just because . . .