Surprisingly, Christmas wasn't ruined this year.
My mother did try, though.
When my brother in law presented the baked pumpkins he had made, she told a "funny" anecdote about how everyone looks forward to pumpkin season in autumn but is sick of pumpkins by Christmas.
When my sister in law told about their church visit and my MIL chimed in about how nice the pastor at that church is, my mother brought up the Catholic church child sexual abuse scandal.
Then she started to rant about Trump. Granted, she despises Trump, but we're having a Christmas dinner in the middle of Germany, we don't want to hear about all he's done which we can do nothing about.
Luckily everyone knows how to deal with it by now, we just go quiet and let her talk until she runs out of steam and then someone suggests to switch to another topic.
Oh man my mother was on one too last week. She was talking about wanting to take a trip to Europe but not being sure about it, I mentioned how she had mentioned she always wanted to go see Prague, and she took that as an opportunity to go on a tangent about the Holocaust. Took four tries to derail her. In the middle of a restaurant too.