Without getting into the ins and outs of the ‘Is Christmas pagan?’ debate, it’s worth dealing with some faulty assumptions people often make about the ‘Christianisation’ of pre-Christian traditions (buckle up for the thread…)
First of all, language people use in this area can be quite emotive, e.g. talk of Christians ‘usurping’ or ‘sanitising’ a pre-existing pagan festival. There’s a tendency to ascribe a collective agency that never existed to ‘the Church’ or ‘Christians’ when it comes to Midwinter
That wasn’t how it worked; there was no centralised programme of reforming popular festivities. The Church introduced liturgical celebration of Christmas to northern pagan cultures; how those Christianised cultures then dealt with Midwinter festivities as a whole varied widely
The minds and behaviour of early medieval people weren’t software programmed by a Church that exercised total control. The Church showed sporadic interest in popular celebrations, but its main concern was Christian rites and belief - not suppressing all pre-Christian legacies
(By the way, it’s always a bit perilous to apply the term ‘pagan’ to pre-Christian legacies, because we know so little about pre-Christian religion we have no reliable way of distinguishing between *specifically religious* pre-Christian customs and others)