It was easy to convert many pagans to Christianity since paganism didn't work but for a few.
Your right, in 392 Theodosius prohibited Paganism, and in true Christian form... the destroyed all the Pagan Temples
and killed the practicing Pagans hahahahaha
Prior to the christians doing such , the pre -Jesus monotheistic Jews had gone around the lands doing a lot of destroying
of the ways of pagan worship, cause they had an agenda > to eliminate rival Gods and centralise control with their mono-God system.
Norse kings eventually supported conversion of pagan vikings to christianity for much the same reason... control.
I mean why have autonomous/independent groups of pagan Norseman conquering, destroying, raping, pillaging, enlsaving , etc
when you can have a program of centralised control of such under one Christian Norse king?
How pagan vikings played the game with christinanity;
https://www.historyonthenet.com/vikings-from-pagans-to-christians.there are 8 or 9 different holidays celebrated during November and December plus New Years day. About 1/2 of them religious.
There is absolutely nothing wrong with saying "Happy Holidays" at this time of year. Having one phrase to cover them all makes a lot of sense. .
I like the term 'festive season' Nov - Jan.