As a game developer, I can see how this accidentally happened. Making games and trailers, you put in placeholder art that doesn't really matter until you get the final work in, so that you can at least get started on something. With sound effects, for example, I've learned to get some sort of sound in as quickly as possible so that you have SOME feedback, and then as you playtest and iterate, you can create your own sound effects/assets as you get further away from prototyping. For example, with that painting, early on in the trailer process, they probably didn't know for sure that that shot would be in the final trailer, so instead of having an artist potentially waste a bunch of time making an art asset, you grab something off google as placeholder to see if the shot even works. Don't waste your time polishing a (potential) turd.
Now, that said, they should have been aware of what was placeholder, so that they could replace it before actually launching the trailer. But I could see how things slip through the cracks. And they apologized and changed it, so good on them.
Yup, all the time. It's how you quickly iterate and prototype.
See: this tweet, showing an early version of Firewatch, with dialogue from the terrible movie The Room, as placeholder dialogue:
https://twitter.com/Nelsormensch/status/701857597872173056