I thought this was going to be an event where people without families or something join the same online space over the holidays. Has that been done?

I don't remember being done explicitely for estranged people, but World of Warcraft has a Christmas event every year, with decorations, special items and thematic quests that you would do alongside other players. You probably can find similar things in other popular MMOs. In a similar way, I'm sure online virtual worlds like Second Life or VRChat have players organizing themed parties and such. Then you also have streamers who do a special stream on Christmas Eve, so in a way their communities are also together during the Holidays.