By the way, what kind of event was Christmas originally?

And I don't mean "It's a holy man's birthday" or "It's when old men get into flashy costumes to ride reindeer and bring presents to children".

Well, those impressions exist because it's a mix of many different things.

The winter solstice is the time of year when the days are shortest and the nights are longest. In other words, it's the season of death. The boundary between the living and dead is at its thinnest as well.

Originally, presents were tributes to keep the dead at bay. Winter was always a season of gift-giving.

To children?

Yeah, just like Halloween. Children are the ones closest to the dead, after all.

Over time, Western religion blended with... or intentionally rewrote the old traditions, creating Christmas.